Istanbul (CNN) Eighteen Saudis are being investigated on the charge of "intentional homicide with premeditation" and torture over the killing of Saudi journalist Jamal Khashoggi, a senior Turkish official with knowledge of the investigation told CNN.
Saudi Arabia initially said Khashoggi had left the Saudi consulate in Istanbul alive on October 2, then claimed he had died in a fistfight there with Saudi officials. The Saudi attorney general said Thursday that Khashoggi was killed in a premeditated murder.
Turkish President Recep Tayyip Erdogan on Friday demanded that Saudi Arabia reveal the location of Khashoggi's body and hand over the suspects.
The Istanbul prosecutor's office has submitted an extradition request to Saudi Arabia for the 18 suspects, who have not been charged.
Saudi Foreign Minister Adel Al-Jubeir indicated Saturday the request would be denied.
"The individuals are Saudi nationals," he said. "They're detained in Saudi Arabia, and the investigation is in Saudi Arabia, and they will be prosecuted in Saudi Arabia."
Saudi Crown Prince Mohammed bin Salman said earlier this week in Riyadh that the kingdom would "implement all necessary rules and investigate deeply in order to achieve results. And to bring to justice those who are responsible for this heinous crime, and they will be put before courts."
Riyadh has maintained that neither bin Salman nor King Salman knew of the operation to target Khashoggi, a former Saudi insider who wrote critical columns for The Washington Post.
US officials have said such a mission, including 15 men sent from Riyadh, could not have been carried out without the authorization of bin Salman, the country's de facto ruler.
Speaking at the International Institute for Strategic Studies Manama Dialogue in Bahrain, Al-Jubeir urged the public to wait for a complete investigation.
"There has been a hysteria in the media about Saudi Arabia's guilt," he said. "People have assigned blame on Saudi Arabia with such certainty before the investigation is complete. We have made it very clear that we are going to have a full and very transparent investigation, the results of which will be released."
Asked how the murder was carried out without the knowledge of bin Salman, Al-Jubeir reiterated that the investigation is ongoing.
"We're trying to uncover what happened," he said. "We know that a mistake was committed, we know that people exceeded their authority, and we know that we are investigating them."
Al-Jubeir added that those responsible would be punished and prosecuted in Saudi Arabia and that "mechanisms will be put in place to ensure this doesn't happen again."
Meanwhile, US Defense Secretary James Mattis, at the same event in Bahrain, said Khashoggi's murder should "concern us all greatly."
"As US Secretary of State Pompeo stated, the US does not tolerate this kind of ruthless action to silence Mr. Khashoggi, a journalist, through violence," he said. "Failure of any one nation to adhere to international norms and rule of law undermines regional stability when it is needed most."
Mattis said US President Donald Trump had noted that the United States would "get to the bottom of it" and added that the President had called for congressional involvement.
Pompeo has vowed to revoke the visas of those responsible and "will be taking additional measures as the situation is clarified," Mattis said.
Turkish Justice Minister Abdulhamir Gul said Friday that Turkish institutions were capable and determined in their investigation, according to Turkey's state news agency Anadolu.
Gul also said Turkey wants its extradition request fulfilled since "this atrocious incident happened in Turkey," Anadolu said.
On Friday evening, a private company used robotic cameras to look into the sewer outside the Saudi consulate in Istanbul.
"The manhole cover was removed by the staff in the van and robotic cameras were lowered into the sewer. The examination carried out in the sewer was monitored in the screens in the van. The van left the street after the examination was over, " Turkish state media Anadolu reported.
The company that did the search told CNN the system was designed to spot the tiniest materials. The search was commissioned by the Turkish government's Water and Sewage Administration, the company said, and was regarding the Khashoggi case.