Up to 200 people have been killed in an attack on the Syrian village of Tremseh, opposition activists say.
Residents told the activists that the village, in Hama province, was attacked with helicopter gunships and tanks.
Pro-government Shabiha militia later went in on foot and carried out execution-style killings, they said.
State media said "terrorist groups" had carried out a massacre to raise tensions ahead of a UN Security Council meeting on the Syria observer mission.
If it is confirmed, the Tremseh attack would be one of the bloodiest single events in the Syria conflict.
Some 16,000 people are thought to have been killed since the uprising against Bashar al-Assad's regime began in March 2011.
Individual reports of casualties often cannot be independently verified, as Syria severely restricts journalists' freedom of movement.
High-level defection
Reports suggest the army was trying to take back Tremseh after it had fallen into rebel hands.
The BBC's Jim Muir in Beirut says both sides agreed many people were killed in Tremseh, but have totally different versions of what happened.
Activists say government forces surrounded the village on Thursday morning and heavily bombarded it for several hours, killing many people.
Pro-government militias from nearby Alawite villages then moved in, they said, killing many more villagers and setting fire to houses. Others who tried to flee through fields were also gunned down, the activists said.
State media said gunmen from what they termed armed terrorist groups had attacked the village in the morning, shooting dead dozens of people.
