MASAYA, Nicaragua (Reuters) - Violent clashes in Nicaragua flared on Friday night at a church in the capital where several people were seriously injured, following months of unrest pitting pro-government forces against protesters that has claimed some 300 lives.

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The clashes between forces that support President Daniel Ortega and demonstrators calling for his resignation mark the deadliest protests in Nicaragua since its civil war ended in 1990.

At the Divine Mercy Catholic Church in Managua, at least three people were injured, according to a post on Twitter by Paulo Abrao, an official with the Inter-American Commission on Human Rights.

One of the injured has been shot through the leg, a Washington Post reporter at the church posted on Twitter, and along with others was allowed out by police and met by waiting ambulances.

It was unclear how many people remained trapped in the church where earlier in the evening gun shots prevented those inside from leaving.

At the National Autonomous University of Nicaragua, also in the capital, some students barricaded themselves on the campus earlier in the day as paramilitary groups that support Ortega shot at the building from outside, according to media reports.

It was not clear how many people had been injured at the university.

Nicaragua has been convulsed by unrest since April when its leftist president proposed reducing pension benefits to cover a social security shortfall. The plan, later dropped, provoked deadly demonstrations and led to demands for Ortega’s resignation and early elections.

A nation-wide strike emptied streets on Friday as businesses shut their doors, heeding the call of civil society groups that have demanded Ortega’s resignation after more than three months of bloody civil unrest.

The general strike followed mass protests that fanned out across the Central American nation on Thursday.

Throughout the day on Friday, television showed deserted streets in Managua and much of the rest of the country while Ortega and his entourage attended a traditional march in the legendary revolutionary stronghold of Masaya, the city from which rebels launched an attack on dictator Anastasio Somoza in 1979.

In brief remarks, Ortega said he lamented the crisis and offered to hold talks with opponents of his government.

“I invite (protesters) to end the confrontation and that all of us unite to give people the peace that Nicaragua needs,” he said, flanked by supporters.

Ortega, a Cold War-era U.S. foe, is serving his third consecutive term which runs until 2021.

Representatives of civil society organizations have called for early elections to end the impasse, while Ortega’s top diplomat dismissed the possibility on Friday during a session of the Organization of American States in Washington.

“You can’t strengthen the country’s institutions, you can’t strengthen the country’s democracy by violating its constitution ... and impose the will of groups that seek a change of government,” said Foreign Minister Denis Moncada.