Shelling by Syrian forces has killed 34 people according to the British-based group the Syrian Observatory for Human Rights.
The organisation says there are children among the dead in the town of Souran in the central province of Hama.
It cited residents saying: "The army shelled the town and then stormed it," according to Reuters.
In a separate incident there was an explosion near a convoy carrying the head of the UN mission in Syria.
There are no reports of casualties in that case and it is not clear if it was a bomb or a rocket-propelled grenade.
Front blown off
Maj Gen Robert Mood's vehicle was at an army checkpoint in the Douma district of Damascus when the blast happened.
Journalists who were in Gen Mood's convoy say the front of a nearby Toyota pick-up vehicle was blown off in Sunday's incident.
There is so far no comment from the mission itself.
Violence between armed rebels and the Syrian army has been escalating despite a truce negotiated by UN-Arab League envoy Kofi Annan.
The Syrian Observatory for Human Rights called the deaths in Hama a "massacre" and urged the UN mission to deploy observers to the area immediately.
Clashes had been reported in Douma earlier in the day. Reuters news agency says gunmen wounded 29 members of the security forces.
The BBC is unable to confirm reports due to tight restrictions on the movements of journalists in Syria.
Douma, on the outskirts of the capital Damascus, was one of the first areas to join the uprising against President Bashar al-Assad last year.
Earlier this month Gen Mood, a Norwegian officer, was in another convoy which avoided an explosion near the city of Deraa.
In that case a Syrian military truck which was escorting the vehicles was hit just seconds after UN staff had passed by.
There are 257 unarmed UN observers in Syria and that number is expected to increase to 300 by the end of May.