Hundreds of gunmen ambushed a convoy of police officers in Syria and killed around 80 personnel, the SANA news agency reported.
The incident took place in Jisr al-Shughour in Idleb province, when the policemen were on their way to control an unrest.
Armed groups also attacked a security centre and a number of government buildings and burned down a few of them.
The insurgents stole around five tonnes of dynamite from a storage building.
Security reinforcements have reached the area to protect civilians, SANA reported.
Syria has been engulfed since March with a wave of protests, calling for reforms and more freedom in the country.
President Bashar al-Assad had initially responded to the anti-government protests by offering some concessions, including lifting the emergency in place since 1963, releasing hundreds of political detainees and reshuffling the government.