Thousands of people marched yesterday in Nicaragua to demand that President Daniel Ortega step down. The demonstrations over proposed benefit cuts, which began three months ago, are expected to continue today.

Human rights groups say about 300 people have been killed during the protests, many by police.

U.S. Senator Marco Rubio has warned that deadly clashes in Managua could lead to civil war, and worsen the immigration crisis in the U.S.

Anti-government marchers demand the resignation of President Daniel Ortega and the release of political prisoners in Managua, Nicaragua, Sunday, July 22, 2018. Anti-government protests began in mid-April over cuts to the social security system but broadened to include demands for Ortega to leave office and for early elections to be held. Arnulfo Franco/AP

CBS News correspondent Manuel Bojorquez reports an eerie quiet during much of the day in the capital city of Managua, as people stay home and business owners close up shop for their own safety.

But after the calm, the sounds of protest pierce the air, and the fear of bloody confrontations returns.

Within minutes of arriving in the capital, Bojorquez encountered an anti-government protest and the sound of mortar fire.

Several young men – masked and holding homemade mortar launchers – told Bojorquez they fire the mortars to warn fellow demonstrators when pro-government forces are near.

They told Bojorquez that they were willing to risk their lives: "The fear is gone," one said.

Masked protesters in Managua, Nicaragua. CBS News

The fear was gone on April 19 – that's the day protests started over proposed cuts to social security benefits. Government forces are accused of killing more than 40 people that week. Hundreds have been killed since then, some even attacked while hiding in a church.

The uprising continues to intensify against President Ortega, whom demonstrators say has turned into a dictator and should step down. But Ortega remains defiant, insisting the protesters are being influenced by outside forces and blaming them for initiating the violence.

Supporters of Nicaragua's President Daniel Ortega hold pictures of dead police officers, who lost their lives during recent protests, at a demonstration in Managua, Nicaragua July 21, 2018. JORGE CABRERA/REUTERS

In the neighborhood of Monimbo, which had been a stronghold of the opposition, barricades built using cobblestones from the streets can still be seen. It was the site of a bloody confrontation with police last week. At this point, it's still not clear how many people were killed.

One woman feared being identified on camera, but wanted to let Bojorquez know one thing: her neighborhood was not backing down – that Monimbo had lost the battle, but not the war.

Several international organizations have called on the Nicaraguan government to end the violent suppression of protests and for President Ortega to allow early elections next year. He refuses to back down, which means the protests are likely to continue.