BEIRUT –Syrian security forces fought gunmen in battles that left over 120 members of the security forces dead, state television said, in the first such report of large-scale armed fighting in the country's revolt.

The television said on Monday armed groups had set government buildings ablaze in the northwestern town of Jisr al-Shughour, stole five tonnes of dynamite and were firing at civilians and security using machineguns and rocket-propelled grenades.

"The security forces have managed to end a blockade of one of the neighbourhoods that was seized by the gunmen for a while and are now battling them to end the blockade of the other neighbourhoods," it said.

"The gunmen mutilated some of the bodies and threw some into the river. The people in Jisr al-Shughour are urging the army to intervene speedily," it said.

Interior Minister Mohammad Ibrahim al-Shaar said authorities would respond firmly to armed attacks and Information Minister Adnan Mahmoud said army units, which had so far stayed out of the town, "will carry out their national duty to restore security".

Opposition activists earlier said a security operation had been under way in the town since Saturday in which they said at least 37 residents and 10 police had been killed.

Syria's SANA news agency said "gangs" entrenched in some areas were using machine guns and hand grenades, noting that residents had made distress calls on the army to intervene.

Syria has been engulfed since March 15 in a wave of protests which called for reforms and more freedom in the country.

Syrian President Bashar al-Assad has responded to the country's unprecedented anti-government protests by offering some concessions, including lifting the state of emergency which had been in place since 1963, releasing hundreds of political detainees and reshuffling the government.