Syrian troops killed three armed dissidents in clashes that erupted during a raid in the northwestern town of Banash, in Idlib province, on Thursday, said the Syrian Observatory for Human Rights.
"The Syrian army backed by tanks and armoured troop carriers launched an assault this morning on the town of Banash and clashes took places with armed men who were apparently dissidents," the rights group said.
"Several houses were partly destroyed and people were wounded... while the noise of heavy machineguns and explosions could be heard in several parts of the town and ambulances seen racing through the streets.
"Three men were killed this morning in Banash town during the military operations," the observatory said, adding that the army had also launched an attack on Taum village, east of that town."
The Local Coordination Committees, which act as umbrella groups for protesters seeking to bring down President Bashar al-Assad, said soldiers and security forces had also carried out a raid on the central district of Homs. Heavy gunfire could be heard.
The Observatory said the military and security agents had set up many checkpoints in the town and arrested 19 people.
On Wednesday, thousands of Syrians who back the president rallied in the centre of the capital, Damascus, to show support for the regime which has faced nearly seven months of popular protests and demands for Assad to quit.
In apparent response to the loyalist rally, anti-regime protests erupted in Idlib in the northwest, in the port of Latakia, Homs, Deir Ezzor in the east, Daraa in the south and near Damascus, the Observatory said.
On Wednesday, a court in the capital freed on bail prominent dissident Walid al-Bunni, who was arrested in August, his lawyer Michel Shammas said.
"The Damascus court of appeals on Wednesday freed opposition figure Walid al-Bunni in exchange for a bail of 1,150 Syrian pounds ($23). He will be tried later for inciting (anti-regime) demonstrations and sectarianism," he said.
Bunni was detained on August 6 along with his two sons, who were released shortly afterwards.
In 2000, Bunni was one of the prime movers of the short-lived "Damascus Spring" amid hopes for reform that followed Assad's accession to the presidency after the death of his father, Hafez.
Reforms were promised but never came, and according to the United Nations the regime's crackdown on protests that began in mid-March has resulted in the deaths of more than 2,900 people.
Syrian authorities blame gangs of armed terrorists for the unrest.