MANAGUA, Nicaragua -- Pro-government forces have seized a major opposition stronghold in Nicaragua. In a violent bid to silence protesters, police and gunman loyal to President Daniel Ortega launched a sweeping crackdown in the city of Masaya on Tuesday.

Juan Sebastian Chamorro, executive director of the Nicaraguan Foundation for Economic and Social Development, called the situation in Nicaragua "extremely dire" and said the country is facing a "humanitarian crisis."

"More than 300 people have been killed in the streets of Nicaragua. More than 2,000 people have been wounded. A hundred and fifty people have been unaccounted for," he said. "And as you can see in the images, you can see soldiers with heavy weapons, live ammunition, weapons that are used for war, shooting against the population that are using just slingshots and house-made mortars and stones."

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Protests against cuts to the social security system that began three months ago have since became a broader call for Ortega to leave office.

Ortega's government has dismissed opponents as delinquents attempting a coup d'etat. He wanted to quell unrest in Masaya before this week's three-month anniversary of the start of protests across Nicaragua.

Chamorro warned that a peaceful resolution needs to be found soon.

"The history of Nicaragua is full of episodes of civil war, and this is precisely what at the national dialogue, mediated by the Catholic Church, are trying to avoid," Chamorro said. "We are trying to avoid another civil war in the country and trying to bring and negotiate a peaceful and democratic solution."

The United States, United Nations and Inter-American Commission on Human Rights have condemned the violence.