Activists say shells and gunfire from Syrian security forces have killed at least 33 people in the city of Hama.
Dozens have reportedly also been injured in two northern districts.
EU foreign ministers meanwhile imposed a new round of sanctions, banning the export of luxury products and goods that could be used to repress dissent.
UK Foreign Secretary William Hague said Damascus was "not in full compliance of the ceasefire requirements" of the peace plan negotiated by Kofi Annan.
Meanwhile, state media reported that "terrorists" had killed a doctor and two military officers in the country's south.
In a separate development, a Jordanian relief agency said Syrian troops had attacked about 900 people trying to flee over the border near the Jordanian town of Ramtha early on Sunday.