United Nations observers have been blocked by Syrian troops from the site of a new mass killing, the head of the monitoring team said today.
General Robert Mood said some UN patrols were also stopped by civilians in the area and that observers were informed by residents that their safety would be at risk if they entered Mazraat al-Qubair in central Hama province.
Syrian opposition groups say pro-government militiamen killed dozens of people, including women and children, in Mazraat al-Qubair last night, with some stabbed to death and others burned.
The exact death toll and circumstances remain impossible to confirm.
The Britain-based Observatory for Human Rights said dozens were killed, and the Local Co-ordination Committees group said more than 78 people died, including many women and children.
It said pro-government militiamen known as shabiha first shelled the farming area and then went in and killed the residents.
Syria's main opposition group in exile, the Syrian National Council, also said 78 people were killed. It said 35 were from the same family and more than half were women and children.
It said the militiamen converged on Qubair from neighbouring pro-regime villages. It said some of the dead were killed execution-style, and others were attacked with knives.
The violence comes on the heels of a horrific massacre in late May in Houla, a cluster of villages in central Homs province, which left more than 100 dead including many children and women gunned down in their homes.
UN investigators blamed pro-government gunmen for at least some of those killings but the Syrian regime denied responsibility and blamed rebels for the deaths.
The Houla massacre triggered international outrage and a co-ordinated expulsion of Syrian diplomats from world capitals.
Syria denied the reports of a new massacre as "absolutely baseless", blaming "an armed terrorist group" and claiming the death toll was nine women and children.
Gen Mood said the mission "is concerned about the restriction imposed on its movement as it will impede our ability to monitor, observe and report".
US secretary of state Hillary Clinton condemned the Syrian government for "simply unconscionable" violence, accusing president Bashar Assad of intensifying a crackdown that has already killed thousands.
"The regime-sponsored violence that we witnessed again in Hama yesterday is simply unconscionable. Assad has doubled down on his brutality and duplicity, and Syria will not, cannot, be peaceful, stable or certainly democratic until Assad goes."
Amateur video posted on the internet purported to show the bodies of babies, children and two women wrapped in blankets and lined with frozen bottles of water to slow their corpses from rotting in a large room with brightly patterned red carpet.
Another row of bodies lay elsewhere: a grandmother, a mother, and five siblings and two cousins, according to the video narrator, all wrapped in white sheets, more frozen water bottles tucked between them.
One toddler's arm covered her face. Their names were scrawled on pieces of paper and tucked into their shrouds.
In another video, the camera pans over to four blackened, charred objects too disfigured to be identified as human bodies. The narrator said they were of a mother and two children who were shelled in their home.