Managua - A raid by pro-government forces Sunday left at least 14 people dead in Nicaragua, where hundreds have been killed since unrest broke out in April, a rights group said.

Protesters in the Central American country, who are demanding the resignation of President Daniel Ortega, had barricaded roads in the areas of Diriamba and Jinotepe, 20 kilometers (13 miles) from the opposition bastion of Masaya.

According to videos filmed by residents and posted on social media, heavily armed groups of men in black-hooded civilian clothes were seen on Sunday in the region.

Demolishing the opposition barricades, they entered the municipalities alongside police, who also surrounded the area. Mechanical equipment dismantled the barricades, opening up access to over 350 cargo trucks stranded on the highway in Jinotepe for over a month. "This has been a horror. We have a minimum of 14 dead, but it could be more.

 That includes at least one anti-riot officer, one paramilitary member and two police officers," Vilma Nunez, president of the Nicaraguan Center for Human Rights (CENIDH), told AFP.

"This looked like an occupation army. They wiped out all the barricades. There are more dead whose identities we have not been able to confirm. There are a lot of arrests and injuries. A disaster," she added.

Police blamed "terrorists with firearms" for the deaths of two officers.

"The situation is serious. There is an undue attack by government forces that is causing bloodshed, more death and mourning in our country," said Alvaro Leiva, the executive secretary of the Nicaraguan Association for Human Rights.

The latest unrest comes after Ortega on Saturday ruled out early elections, after previously remaining silent on the proposal by the influential Catholic hierarchy.

Appearing at a rally in the capital Managua, attended by thousands of supporters, Ortega branded his opponents "murderers" and "criminals."

"Down with the coup plotters!", "Not one step backward!", "Stay, my commander stays!", "We want peace," supporters shouted, waving flags of the ruling Sandinista National Liberation Front.

Protesters, who at first took to the streets against now-aborted pension reforms, are demanding the resignation of Ortega - a former leftist guerrilla who came to power with the popular uprising that defeated dictator Anastasio Somoza in 1979, and retook the presidency in 2007 after a vote.

Activists accuse him - together with his wife Vice President Rosario Murillo - of establishing a dictatorship characterized by nepotism and brutal repression.

Roman Catholic bishops, working to mediate dialogue between the government and opposition in a bid to end the crisis, said in the wake of Ortega's declaration that they were "seriously" assessing whether to continue their efforts.

"What sense does it make to continue with the dialogue if the streets continue to be filled with blood," said Cardinal Leopoldo Brenes, president of the Nicaraguan Episcopal Conference.

Meanwhile Silvio Baez, auxiliary bishop of Managua, said it is not possible to negotiate with "representatives of a government that lies, does not accept responsibility and continues attacking and massacring the population."