Paris(CNN) Authorities are hunting for a Belgium-born French national who's one of three brothers suspected in the Paris terror attacks.
Belgian and French officials want to know where Salah Abdeslam is, and Belgium has issued an international warrant for him.
French police released his photo and warned people not to interact with him, saying that he is dangerous.
Salah Abdeslam is suspected of being involved in the attacks.
Investigators haven't said much about how they believe Abdeslam is tied to Friday's series of shootings and explosions in the French capital.
Jean-Pascal Thoreau, a spokesman for Belgium's Federal Prosecutor, said Abdeslam is one of three brothers suspected of involvement in the attacks. One of the brothers was killed in the attacks, and another was arrested by Belgian police, Thoreau said.
Salah Abdeslam had been questioned by French police earlier but was not detained, a source close to the investigation into the Paris attacks said.
He was driving in the direction of the Belgian border when stopped by police and questioned a few hours after the attacks, the source said. Now, his whereabouts are unknown.
International manhunt for terror suspect, 150 raids across France
The Paris attacks killed at least 129 people and wounded more than 350 others, many of them seriously.
Names of victims start to emerge
The Islamic terror group ISIS has claimed responsibility for the slaughter, which France's President described as "an act of war."
French fighter jets struck ISIS targets in the Syrian city of Raqqa on Sunday in what officials called a major bombardment and analysts described as a retaliatory move. Authorities made a number of arrests linked to the attacks in Belgium, and investigators homed in on an abandoned car with weapons found in eastern Paris.
Two days after the Paris attacks, the French capital is a city in mourning -- and on edge -- with key questions looming: Do suspects remain at large? Could another attack be in the offing? And how will France and other countries respond?
Night of terror: Paris attacks
A forensic scientist works near a Paris cafe on Saturday, November 14, following a series of coordinated attacks in Paris the night before that killed scores of people. ISIS has claimed responsibility.
Police are out in force November 14 near La Belle Equipe, one of the sites of the terror attacks.
Forensic police search for evidence inside the Comptoir Voltaire cafe after the attacks.
Shoes and a bloody shirt lie outside the Bataclan concert hall on November 14. Most of the fatalities occurred at the Bataclan in central Paris.
Security forces evacuate people on Rue Oberkampf near the Bataclan concert hall early on November 14.
Medics evacuate an injured woman on Boulevard des Filles du Calvaire near the Bataclan early on November 14.
Police, firefighters and rescue workers secure the area near the Bataclan concert hall on November 14.
A man with blood on his shirt talks on the phone on November 14. He is next to the Bataclan theater, where gunmen shot concertgoers and held hostages until police raided the building.
Police officers patrol the area around Notre Dame cathedral in Paris on November 14.
Police officers patrol Paris' Saint-German neighborhood on November 14.
Victims of the shooting at the Bataclan concert venue in central Paris are evacuated to receive medical treatment on November 14.
A woman is evacuated from the Bataclan theater early on November 14.
Forensics are working in the street of Paris after the terrorist attack on Friday, November 13. The words "horror," "massacre" and "war" peppered the front pages of the country's newspapers, conveying the shell-shocked mood.
Rescuers evacuate an injured person near the Stade de France, one of several sites of attacks November 13 in Paris. Thousands of fans were watching a soccer match between France and Germany when the attacks occurred.
A survivor of the terrorist attack in the Bataclan is assisted following terror attacks, November 13. The violence at the Bataclan, which involved a hostage-taking, resulted in the highest number of casualties of all the attacks.
Spectators invade the pitch of the Stade de France stadium after the international friendly soccer match between France and Germany in Saint-Denis.
Spectators embrace each other as they stand on the playing field of the Stade de France stadium at the end of a soccer match between France and Germany in Saint-Denis, outside Paris, on November 13.
A body, covered by a sheet, is seen on the sidewalk outside the Bataclan theater.
Rescuers evacuate an injured person on Boulevard des Filles du Calvaire, close to the Bataclan concert hall in central Paris.
Wounded people are evacuated outside the scene of a hostage situation at the Bataclan theater in Paris on November 13.
A medic tends to a wounded man following the attacks near the Boulevard des Filles du Calvaire.
A woman walks past police and firefighters in the Oberkampf area of Paris.
A riot police officer stands by an ambulance near the Bataclan concert hall in central Paris.
Wounded people are evacuated outside the Bataclan concert hall.
Police secure the Stade de France in Saint-Denis, north of Paris, following explosions during the soccer match between France and Germany.
A wounded man is evacuated from the Stade de France in Saint-Denis, outside Paris.
Spectators gather on the field of the Stade de France after the attacks. Explosions were heard during the soccer match between France and Germany.
French security forces rush in as people are evacuated in the area of Rue Bichat in the 10th District of Paris.
People leave the Stade de France after explosions were heard near the stadium during a soccer match between France and Germany on Friday. Paris Deputy Mayor Patrick Klugman told CNN President Francois Hollande was at the match and was evacuated at halftime.
Victims lay on the pavement outside a Paris restaurant.
Rescue workers and medics tend to victims at the scene of one of the shootings, a restaurant in the 10th District. Attackers reportedly used AK-47 automatic weapons in separate attacks across Paris, and there were explosions at the Stade de France.
French security forces move people in the area of Rue Bichat in the 10th District. A witness told BFMTV that firefighters were on the scene to treat the injured.
Hiding among refugees?
It's possible suspects who were directly involved in the attacks remain at large, a French counterterrorism source close to the investigation told CNN.
While investigators pieced together information about who could be on the loose, details emerged about several of the seven attackers who authorities say were killed:
• At least three of the terrorists involved in the attacks had spent time in Syria, a French official told CNN Sunday. The official did not identify the attackers.
• One of three bombers who detonated themselves at the Stade de France late Friday arrived on the Greek island of Leros on October 3 among numerous Syrian refugees, CNN's Christiane Amanpour reported, citing an unnamed French senator who was briefed by the Ministry of the Interior.
World reacts to Paris attacks
President Barack Obama, French President Francois Hollande, second from right, and Paris Mayor Anne Hidalgo arrive at the Bataclan, site of one of the Paris terrorists attacks, to pay their respects to the victims after Obama arrived in town for the COP21 climate change conference early on Monday, November 30, in Paris.
The Eiffel Tower in Paris is illuminated in the French national colors on Monday, November 16. Displays of support for the French people were evident at landmarks around the globe after the deadly terrorist attacks in Paris on Friday, November 13.
People hold hands as they observe a minute of silence in Lyon, France, on November 16, three days after the Paris attacks. A minute of silence was observed throughout the country in memory of the victims of the country's deadliest violence since World War II.
French President Francois Hollande, center, flanked by French Prime Minister Manuel Valls, right, and French Education Minister Najat Vallaud-Belkacem, center left, stands among students during a minute of silence in the courtyard of the Sorbonne University in Paris on November 16.
A large crowd gathers to lay flowers and candles in front of the Carillon restaurant in Paris on Sunday, November 15.
A man sits next to candles lit as homage to the victims of the deadly attacks in Paris at a square in Rio de Janeiro on November 15.
People light candles in tribute to the Paris victims on November 15 in Budapest, Hungary.
People gather outside Notre Dame Cathedral in Paris on November 15 for a national service for the victims of the city's terror attacks.
People write messages on the ground at Place de la Republique in Paris on November 15.
People pray during a candlelight vigil for victims of the Paris attacks at a church in Islamabad, Pakistan, on November 15.
French golfer Gregory Bourdy passes a peace symbol for the Paris victims during the BMW Shanghai Masters tournament November 15 in Shanghai, China.
A man offers a prayer in memory of victims of the Paris attacks at the French Embassy in Tokyo on November 15.
A woman holds a candle atop a miniature replica of the Eiffel Tower during a candlelight vigil Saturday, November 14, in Vancouver, British Columbia.
Front pages of Japanese newspapers in Tokyo show coverage and photos of the Paris attacks on November 14.
An electronic billboard on a canal in Milan, Italy reads, in French, "I'm Paris," on November 14.
The Eiffel Tower stands dark as a mourning gesture on November 14, in Paris. More than 125 people were killed in a series of coordinated attacks in Paris on Friday. People around the world reacted in horror to the deadly terrorist assaults.
Lithuanians hold a candlelight vigil in front of the French Embassy in Vilnius, Lithuania, on November 14.
Thousands gather in London's Trafalgar Square for a candlelit vigil on November 14 to honor the victims of the Paris attacks.
A woman lights candles at a memorial near the Bataclan theater in Paris on November 14.
A man places a candle in front of Le Carillon cafe in Paris on November 14.
A woman holds a French flag during a gathering in Stockholm, Sweden, on November 14.
Nancy Acevedo prays for France during the opening prayer for the Sunshine Summit being held at Rosen Shingle Creek in Orlando, Florida on November 14.
French soldiers of the United Nations' interim forces in Lebanon observe the national flag at half-staff at the contingent headquarters in the village of Deir Kifa on November 14.
A couple surveys the signature sails of the Sydney Opera House lit in the colors of the French flag in Sydney on November 14.
A woman places flowers in front of the French Consulate in St. Petersburg, Russia, on November 14.
Candles are lit in Hong Kong on November 14 to remember the scores who died in France.
A woman lights a candle outside the French Consulate in Barcelona, Spain, on November 14.
Britain's Prince Charles expresses solidarity with France at a birthday barbecue in his honor near Perth, Australia, on November 14.
The French national flag flutters at half-staff on November 14 at its embassy in Beijing.
Dutch Prime Minister Mark Rutte after a speech on November 14 in The Hague following the attacks.
Japanese Prime Minister Shinzo Abe becomes emotional after his speech on the French attacks during the opening ceremony of a Japanese garden in Istanbul, Turkey, on November 14.
A woman mourns outside Le Carillon bar in the 10th district of Paris on November 14. The attackers ruthlessly sought out soft targets where people were getting their weekends underway.
People lay flowers outside the French Embassy in Moscow on November 14.
Mourners gather outside Le Carillon bar in the 10th district of Paris on November 14. "We were listening to music when we heard what we thought were the sounds of firecrackers," a doctor from a nearby hospital who was drinking in the bar with colleagues told Le Monde. "A few moments later, it was a scene straight out of a war. Blood everywhere."
People attend a vigil outside the French Consulate in Montreal. Prime Minister Justin Trudeau offered "all of Canada's support" to France on Friday, November 13, in the wake of the attacks.
Police show a heightened presence in Times Square in New York on November 13, following the terrorist attacks in Paris.
People light candles at a vigil outside the French Consulate in Montreal on November 13.
University of Nevada, Las Vegas, fans observe a moment of silence for the victims of the terrorist attacks in Paris before a basketball game November 13.
The house lights are shut off and scoreboard dark as Boston Celtics players pause for a moment of silence for the Paris victims before an NBA basketball game against the Atlanta Hawks in Boston on November 13.
People light candles at a vigil outside the French Consulate in Montreal on November 13.
The senator told CNN that the man was carrying a fake or doctored Syrian passport, and also a registration document for refugee status issued by Greek authorities. The fingerprints taken by Greek authorities match those of the terrorist who blew himself up at the Stade de France, the senator said.
• Bilal Hadfi, a Belgian resident who is thought to have fought in Syria, was one of the attackers, according to several sources. Hadfi, who was killed in the attacks, was 19 or 20, the sources said.
• One of the suicide bombers has been identified as Ismael Omar Mostefai, according to Jean-Pierre Gorges, the mayor of the French town of Chartres, who is also a member of Parliament. Mostefai lived in Chartres at least until 2012, Gorges said in a Facebook post Saturday.
Paris prosecutor Francois Molins described him as a 29-year-old French citizen with a criminal record from the southern Paris suburbs. The attacker, who was involved in the assault and hostage-taking at the Bataclan concert hall, was identified by fingerprints and was believed to have been radicalized in 2010 but had never been accused of terrorism, Molins said.
Agnes Thibault-Lecuivre, the Paris prosecutor's spokeswoman, told CNN that six people -- all family relatives of Mostefai -- have been detained. It is common practice in criminal cases in France to place family members in custody. Mostefai's relatives have not been charged or arrested.
City on edge
The violence that hit six sites around the city has deepened the trauma for Parisians, who had already been shaken by a series of terrorist attacks in January that left 17 people dead.
People were still out around the city Saturday, some posing for selfies along the Seine or stealing a kiss in front of the Eiffel Tower. But the tower itself -- like many other tourist attractions, shops and public buildings -- has been closed in the aftermath of the attacks.
French President vows 'ruthless' response
Reflecting just how nervous Paris is right now, a panic broke out Sunday evening in a crowd gathered at a memorial erected at one of the sites of Friday's terror attacks.
Video showed mourners suddenly spooked, though it's still unclear why.
People ran away screaming. Some jumped over lit candles of the memorial, others grabbed their children and sprinted away.
The panic ended quickly and police cleared the memorial, saying no one is allowed to gather, at least for the time being.
Security has been stepped up, with military reinforcements drafted in.
There has been an outpouring of support and solidarity in Paris, but large gatherings in the streets have not materialized, partly because the state of emergency prohibits them.
Sadness and fear are taking a toll, Paris Deputy Mayor Patrick Klugman said.
"We don't know yet if this terror in fact is over or not," he told CNN, highlighting the jitters caused by unsubstantiated rumors circulating on social media.
Three Kalashnikovs found in abandoned car
CNN affiliate BFMTV reported Sunday that authorities had found three Kalashnikov automatic rifles in an abandoned car in the eastern Paris suburb of Montreuil that was believed to have been used by perpetrators of the attacks.
It's unclear whether any arrests authorities have made so far are connected to the vehicle, the French counterterrorism source said.
At least seven people have been arrested in raids in Belgium connected to the Paris attacks, officials said. Those arrested were in contact with the Paris attackers, a senior Belgian counterterrorism source told CNN. No weapons or explosives were found on them.
Raids were conducted in a Brussels suburb, Justice Ministry spokeswoman Sieghild Lacoere said. A car rented in Brussels was found near one of the sites of the Paris attacks, which triggered the raids, Lacoere said.
On Saturday, CNN affiliate BFMTV reported that the father and a brother of one of the attackers had been taken into custody. And AFP reported that the two men were detained after police raided their homes 130 kilometers (80 miles) east of Paris. CNN has not independently verified that the men were picked up by authorities.
Complete coverage of Paris attacks
Margot Haddad reported from Paris, Jethro Mullen wrote from Hong Kong, Don Melvin wrote from London and Ashley Fantz wrote from Atlanta. Tim Lister, Catherine E. Shoichet, Steve Almasy, Mariano Castillo, Michael Martinez, Pamela Brown, Evan Perez, Pierre Meilhan and Jim Bittermann contributed to this report.