Forces loyal to Nicaraguan President Daniel Ortega seized on Tuesday the opposition stronghold city of Masaya that had recently become a center of resistance to his government. The capture followed fierce clashes with activists in the flashpoint neighborhood of Monimbo that rights groups say left at least two people dead. Police and government-backed paramilitaries launched the organized attack on Masaya as international calls mounted for an end to months of deadly violence in the Central American country. Youths fired homemade mortars from behind barriers of stacked paving stones pried from streets lined by single-story homes and artisan workshops in the town about 16 miles (26 kilometers) southeast of the capital. But they were overwhelmingly outgunned by government loyalists who within hours had advanced to the heart of the neighborhood and began posting videos on social media of themselves firing semi-automatic rifles into the air in celebration. The government said on its website "today was the turn of Monimbo, Masaya, which now has streets that have been liberated from blockades," adding that now people can "move freely." Alvaro Leiva, secretary of the Nicaraguan Association for Human Rights (ANPDH), told AFP that the pro-Ortega forces had taken control of the city after several hours of combat and "excessive use of force." The head of the Nicaraguan Center for Human Rights, Vilma Nunez, said at least two people were killed -- an adult woman and a police officer. State media confirmed the death of the policeman but gave no other toll from the assault. A group of journalists, including AFP, that tried to enter Monimbo to verify the situation were shot at by pro-government gunmen to prevent them approaching. There were also widespread reports of youth hauled away by pro-government fighters. The same neighborhoods residents rose up against strongman Anastasio Somoza in the late 1970s as part of the Nicaraguan Revolution led in part by Ortega himself. But since protests against cuts to the social security system in mid-April became a broader call for Ortega to leave office, Monimbo had again become a center of the opposition. The offensive on Masaya came on the heels of a bloody siege of student protesters holed up in a church in the capital Managua over the weekend, suggesting Ortega was intensifying the use of lethal force to quell dissent. His government says it is carrying out a "liberation" of towns and cities where protesters have been active. The US warned Ortega against pursuing the assault on Masaya. It called for a halt to the deadly crackdown on anti-government protests that has left some 280 people dead over the past three months. "We strongly urge President Ortega not to attack Masaya," tweeted Francisco Palmieri, the US principal deputy assistant secretary of state for Western hemisphere affairs. "Continued govt-instigated violence and bloodshed in #Nicaragua must end immediately. The world is watching." "They are shooting at houses in an irresponsible way. The message is that anyone who pops their head out will be killed: its a message of terror," said ANPDH head Leiva. On Monday, United Nations Secretary General Antonio Guterres urged an end to the violence and a resumption of the stalled dialogue with the opposition. In Brussels, Paul Oquist -- Nicaraguas minister for national policies and one of the cabinet members closest to Ortega -- told AFP in an interview on Tuesday that an attempted "coup" had been defeated. "That is very good news because what it leaves then is dialogue, because the coup plotters did not want dialogue," Oquist said. The government launched its "clean-up" operation in Masaya this month in a bid to break through barriers of piled bricks and clear opposition activists from the streets. The opposition insists Ortega resign. It has called for elections scheduled for 2021 to be brought forward to next year. A former guerrilla leader, Ortega has been in power since 2007 following an earlier 11-year stint as leader after the 1979 overthrow of US-backed dictator Somoza. The 72-year-old president has dismissed the opposition demands, and doubled down on using force to get his way.