New images which have not been independently verified show at least 16 of the people reportedly killed in heavy shelling on a farming village in central Syria.
Opposition activists say around 200, mostly civilians were killed in Tremseh on the outskirts of Hama.
Residents claim the village was attacked by tanks and helicopters. It happened as the U.N.Security Council meets to negotiate a potentially new resolution on Syria.
U.N. monitors in the country are currently confined to Damascus because of mounting violence.
General Robert Mood, the U.N. monitoring mission chief confirmed there had been continuous fighting. He urged the international powers to unite for the sake of Syrian people and said he would recommend an extension of the mission but with a different orientation, “to make sure that we continue to be on the ground for the Syrian people and with the Syrian people,” he said.
UN and Arab League special envoy for Syria, Kofi Annan said he was “shocked and appalled” by the news. Washington said it showed the need for tougher action, Russia again ruled out such a step. Annan is set for talks in Moscow on Monday.
Syria state media blamed the killings on “terrorist groups.”