(CNN) Mothers and other family members of detained opponents of Nicaraguan President Daniel Ortega fled to the cathedral in Managua after pro-government groups harassed them, said Adelaida Sánchez, a spokesperson for the Nicaraguan Center for Human Rights (CENIDH).
The mothers had been camping outside El Chipote detention center for several weeks awaiting news of their children, mostly students and civil leaders.
Sánchez said the Nicaraguan government ordered the pro-government groups to clear the area around the detention center, prompting many of the mothers to seek refuge in the Managua Metropolitan Cathedral of the Immaculate Conception.
As many as 20 mothers and family members were still inside the church Sunday.
The pro-government groups surrounded the church Saturday afternoon, but no incidents were reported.
CNN spoke to one of the mothers inside, who said they haven't left because they're "afraid of being detained or worse." CNN is not naming the woman because she fears for her safety.
CNN has been trying to get a statement from government authorities, but emails and phone calls have not been answered.
The pro-government groups are a mix of members of the Nicaraguan National Police, plain-clothes activists and paramilitary forces. According to reports by the Organization of American States (OAS), they operate together, sometimes wearing dark clothes and masks.
CENIDH said the people held in the El Chipote detention center are not allowed to receive visits nor seek legal representation. Sánchez said their main concern is the well-being of the detainees, especially after CENIDH confirmed "cases of torture and cruelty" inside the prison.
The detainees in El Chipote are part of the resistance groups against Ortega, who has been in power for 11 years.
They began protesting in April after the government announced changes to the social security system regarding pensions. Although Ortega backed down a few days later, the protests did not stop. The government's heavy-handed response ignited a national movement asking for his resignation.
According to CENIDH, 286 people have died and 2,000 have been injured in the unrest. The government puts the number of victims at more than 50.
A report from the Inter-American Commission of Human Rights (IACHR) published in mid-July stated that they have not been able to confirm the number of protesters detained in Nicaragua. However, IACHR estimated that the numbers could surpass 1,000. IACHR is part of the Organization of American States (OAS).
Ortega's government has called the protesters terrorists and says it's working with groups loyal to the administration in liberating towns and cities across the country.
Nicaragua's National Police have not responded to CNN's request for comment. However, they have previously stated that all efforts to restore peace in the country are being driven by a plan the governments calls "Operación Limpieza," or "Operation Cleaning." The government, however, has not specified what the plan entails or how they operate.
CENIDH says Operation Cleaning is a joint action between police members and armed civilians in which groups "go from town to town, entering homes, detaining protesters and even carrying out extrajudicial executions."
The groups carrying out Operation Cleaning were armed when they stormed Monimbó, a stronghold of the country's anti-government movement in western Nicaragua Tuesday.
The clash, which left the area littered with shell casings and shattered glass, lasted more than four hours and saw protesters armed with homemade mortars pitted against hooded government loyalists with automatic, high-caliber weapons, reporters with CNN said.
Four people were killed in this attack, CENIDH said -- three civilians and one policeman.
In a statement, the Nicaraguan National Police identified the policeman as Kelvin Javier Rivera, saying that he was killed by "terrorist groups." The statement did not make any comments about the civilians killed.
CNN talked to a group of protesters in Monimbó who described the post-attack scene as a "war zone." Carlos Trujillo, US ambassador to the OAS, condemned the forceful intervention in Monimbó, describing the government's actions as "genocide."
"The government's repeated acts of violence and repression will only lead to further isolation and sanctions," he wrote on Twitter.
The government did not refer to the situation in Monimbó as an attack but as a "liberation" and has not made any comments regarding the reported victims.