Nicaraguan government forces have launched raids to clear protesters' barricades in towns in the south-east of the country, leaving at least 10 dead.
Human rights organisations say at least six civilians were killed along with four members of the security forces.
The operation targeted the city of Masaya and several smaller communities and neighbourhoods in the area.
The EU, Colombia, Chile and Ecuador criticised the government's actions.
Alvaro Leiva, the head of Nicaraguan Association For Human Rights (ANPDH), said at least 22 vehicles carrying government security forces had arrived in the area.
Labelled "Operation Clean-up" by the government, it concentrated on the city of Masaya, nearby Niquinohomo and Catarina villages and the neighbourhood of Monimbo.
Mr Leiva warned people in the city of Masaya to stay indoors, saying "there are sharpshooters stationed at different places around the city".
Earlier he said police had not been allowing the wounded to reach hospitals in the area.
One resident in Masaya told the French news agency AFP: "We are being attacked by the national police and paramilitaries armed with AK-47s."
The latest government action came a day after dozens of students in the capital Managua were besieged by pro-government forces for hours in a parish church next to the National Autonomous University of Managua (UNAN) before finally being allowed to leave after the intervention of Catholic Bishops.
Two students died in the action and many said they felt the security forces had been shooting to kill.
The UNAN was the last bastion of student resistance in the capital after months of nationwide anti-government protests in which over 300 people have been killed.
Bishop's car attacked
Also on Sunday, there were reports of attacks on members of the National Dialogue conference trying to resolve the differences between the government and the opposition.
Paramilitaries attacked the car of Abelardo Mata, the Roman Catholic bishop of Esteli, breaking windscreens and windows and damaging the tyres.
The bishop was held for a time in a house and then transferred to Managua by the police.
He is one of the mediators for the Nicaraguan Episcopal Conference overseeing talks between the government and protesters.
In Managua a peasant leader, Medardo Mairena who was arrested last week, and is also a member of the National Dialogue conference, appeared before a judge in a closed court accused of terrorism.
A police statement said he was "responsible for the massacre and murder of four policemen and a primary school teacher as a result of his terrorist actions".
Mr Mairena's brother was shot in the chest on Friday by snipers as he led a protest to highlight his arrest.
The Inter-American Commission for Human Rights, EU and Peru, Chile Colombia, Spain, and Argentina have all published statements rejecting the actions of the Nicaraguan government over the past few days.