(CNN)Two men were killed Friday night in Managua after pro-government forces attacked the National Autonomous University of Nicaragua, the strongest protest holdout in the capital, according to Paulo Abrao, the executive secretary of the Inter-American Commission on Human Rights.
The attack lasted several hours, forcing students from the university, including those already injured, to flee and seek refuge inside the Divine Mercy Church, a small Catholic parish near the student compound.
Later, the church was also hemmed in by gunfire, according to Abrao, sources from Nicaragua's Catholic Church, students and one journalist.
A 20-year-old man died inside the church, Abrao said. The second deceased victim has not been identified and it's not clear whether he died inside the church or while trying to reach Divine Mercy.
Bishop Silvio José Báez tweeted the news of the attack as it started around 8 p.m. ET (6 p.m. local time) Friday.
"They're shooting at the Divine Mercy parish! There is a priest inside and several wounded. Stop the repression!" he tweeted. Minutes later, Báez tweeted that ambulances and first aid teams were not allowed to attend to the wounded inside the church.
Abrao said by telephone that at least 100 students were able to hide inside the church along with three journalists -- Sergio Marín of La Mesa Redonda, Joshua Partlow of The Washington Post and José Noel Marenco of 100% Noticias.
According to Marenco, 15 students were shot. The images he shared online showed a gruesome siege in the middle of darkness.
A group of volunteer doctors that is part of a permanent medical guard inside the church treated some of the injured.
Marenco said other injuries were too severe and required hospitalization.
In the middle of the attack, representatives from the church, including Cardinal Leopoldo José Brenes Solorzano, members of the Inter-American Commission on Human Rights and members of the Red Cross mediated with pro-government groups outside the parish, which led to the entrance late Friday of ambulances and emergency services.
The majority of students and two of the journalists were not able to leave the church until Saturday morning, according to one of the trapped journalists and local media. The Rev. Monsignor Waldemar Stanislaw Sommertag, the Pope's envoy to Nicaragua, had to escort them out.
The Nicaraguan government called those who had been trapped inside the Divine Mercy Church terrorists and has said university students are hiding weapons inside the school to assault pro-government groups.
Last week, during a standoff at a Catholic church in Diriamba, south of Managua, the government made similar claims. The government said the church was allowing protesters to hide guns inside. The Catholic Church of Nicaragua denied the allegations.
The standoff at Divine Mercy Church was the latest in a series of violent clashes that started last April when the Nicaraguan government announced changes to the social security system regarding pensions.
President Daniel Ortega, who is been in power for 11 years, backed down a few days later.
However, the Organization of American States and the Inter-American Commission on Human Rights, which is part of the OAS, said the repression and the number of people killed by government forces ignited a national movement demanding Ortega's resignation.
According to the commission, since the start of the violence, 271 people have died and as many as 2,000 have been injured. The number of dead includes those killed in Friday's attack.
The government of Nicaragua, however, puts the number at 51 victims, including four policemen who died last week in the department of Rio San Juan.
The OAS held two emergency meetings this week to discuss the ongoing violence. Argentina, Chile, Colombia, Paraguay, Peru and the United States demanded an end to the repression.
Venezuela, however, supports Nicaragua and claims the opposition groups are being financed by the US government.
The secretary-general of the OAS, Luis Almagro, proposed early presidential elections as a way out of the crisis. The government of Nicaragua rejected the request.
