(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.

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