At least 21 people were killed in violence across Syria on Sunday, including three children in a village in central Hama province, the Syrian Observatory for Human Rights said.
At least 16 people were killed in the village of Souran in the province of Hama by shelling and gunfire from regime forces, said the Britain-based group, adding that three children were among the dead.
"There is no evidence that there were any clashes taking place in the area," before the deadly shelling took place, the Observatory said.
Five other people were killed in violence elsewhere in the country, the watchdog said, adding that anti-regime demonstrations were also held in several areas of Syria on Sunday.
"A civilian was killed after he suffered gunshot wounds from regime troops, who were raiding Hasraya village" in the central province of Homs, the Observatory said.
In Basra al-Sham city of southern Daraa province, an army defector was killed in an overnight ambush by regime forces, the group said.
In Jisr al-Shughur in northwest Idlib, a flashpoint of unrest, armed men assassinated a Baath party official, the monitor said, amid a marked increase of assassinations targeting people associated with the regime.
"There is definitely an increase in assassinations targeting people associated with the regime, be they officials or pro-regime businessmen," Observatory head Rami Abdel Rahman told AFP in Beirut by telephone.
In Idlib city, a defector was killed during clashes with regime forces.
Meanwhile in Douma, a northern suburb of Damascus, a civilian was killed by sniper fire just after a group of UN truce monitors had visited the area, according to the Observatory.
It also reported demonstrations in several areas of northwest Idlib and in Hama calling for the ouster of President Bashar al-Assad's regime.
In Daraa province, demonstrations were also held calling for the release of activist and citizen journalist Mohammed al-Hariri, who according to Reporters Without Borders (RSF) has been sentenced to death for "high treason."
Hariri was arrested on April 16, RSF said, after he gave an interview to Qatar-based, pan-Arab television channel Al-Jazeera from his home in Daraa province.
The latest demonstrations took place after fierce fighting between regime troops and armed rebels rocked parts of the Syrian capital Damascus overnight, the Observatory said.
"Violent clashes broke out between rebel fighters and regime troops at a checkpoint in Kafr Sousa district," it added.
The Local Coordination Committees, an anti-regime network of activists on the ground in Syria, said that in the wake of the fighting, Kafr Sousa in the south of the capital saw the "arrival of huge reinforcements" of regime troops.
Clashes also broke out in others parts of southern Damascus, the Observatory said, adding that gunfire had during the night echoed across the city centre.
On Saturday, 23 people were killed in violence across Syria, the Observatory said.
More than 12,000 people, the majority of them civilians, have died in Syria since an anti-regime revolt broke out in March 2011, according to the monitoring group.