Syrian regime forces pounded the town of Rastan in central Homs province on Thursday, killing three civilians, said the Syrian Observatory for Human Rights.
Violence elsewhere in Syria killed two other people in the morning, the Britain-based watchdog reported.
Government forces have been trying to overrun Rastan for 11 consecutive days, after rebel fighters from the battered central city of Homs regrouped in the town that straddles the main highway linking Damascus to the north.
Speaking to AFP via Skype on Wednesday, Abu Rawan, an opposition activist in Rastan, said there was no electricity in the besieged town, and a shortage of food and water.
Abu Rawan was not reachable for comment on Thursday morning.
Elsewhere in the violence-swept country, one civilian and regular army soldier were killed in eastern Deir Ezzor province, according to the Observatory.
"Regime forces killed a young man at dawn in Quriya town in Deir Ezzor," it said, adding clashes between rebel forces and regime troops were taking place in the town, leaving dead one soldier.
More than 12,600 people More than 12,600 people have been killed in Syria since a revolt against President Bashar al-Assad's rule broke out in March 2011, including nearly 1,500 since a UN-backed truce took effect on April 12, according to the Observatory.