For the second time in less than a fortnight, forces loyal to President Bashar al-Assad were accused of carrying out a gruesome massacre of innocent men, women and children yesterday as UN monitors, in Syria to watch over a non-existent ceasefire, were denied access to a village where up to 78 people are believed to have been brutally murdered.

As Kofi Annan addressed a half-empty United Nations General Assembly in New York and warned of all-out civil war, both anti- and pro-government factions in Syria blamed each other for the killings at Qubair, a village close to Houla, where more than 100 people were butchered last month.

As diplomats expressed outrage at the attacks, the UN Secretary-General Ban Ki-moon said its monitors had come under small arms fire as they tried to reach the village yesterday afternoon. The Independent has chosen not to publish photographs of the blood-soaked bodies of dead children, which have emerged from the two villages. 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 a brightly patterned red carpet.

Another row of bodies lay elsewhere: a grandmother, a mother, five siblings and two cousins, according to the video narrator, all wrapped in white sheets, more frozen water bottles tucked between them, the Associated Press news agency reported. 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. The narrator said they were a mother and two children.

The Syrian authorities issued a curt denial of the massacre, accompanied by an alternative explanation for the reports of violence. "An armed terrorist group committed an appalling crime," it claimed, saying nine women and children had been killed. But survivors were in no doubt that pro-Assad militias were responsible.

"At two o'clock Syrian time, the regime army started to shell the area using tanks," said Mousab Al Hamadee, who said he was a local activist. "It is typical to start with shelling, then security forces storm the town or the village. In this case there were no security forces, only shabiha [regime militia] in very large numbers. Qubair is similar to Houla in that it is close to Alawite villages.

"They shot people at close distance, burnt people alive in their houses and used knives to slaughter people like sheep. Many people were from the same family, it's very common in these villages for most people to be related. It is a very poor rural area and Qubair itself only has a population of around 150 people. Very few are still alive."

Others claiming to be from the village backed this version of events, describing indiscriminate killing. "They murdered children and women and the bodies were burnt by those thugs... Nobody could bear the horrific scenes of these burnt bodies of children and women..." said an activist giving his name as Laith Al Hamawi. One three- month-old infant was burnt alive, he claimed, adding: "They were all burnt."

It was impossible to verify the accuracy of these claims, although several people purporting to be from the area yesterday gave similar accounts of the atrocity. The UN confirmed that its monitors were denied access to the villages, which prevented the reporting of any independent account of the massacre.

With the stakes in the conflict rising every day, with the US Secretary of State, Hillary Clinton, once again insisting yesterday that President Assad should leave the country, and Russia hinting that it was not now opposed to a change of leadership in the country that is its most important ally in the Middle East, every image of horror from the ground has an unprecedented weight.

However, those claiming to be from the village said that the monitors had ignored initial pleas for assistance. Mr Al Hamawi said: "I called UN monitors to come to stop the massacre but they didn't come – they didn't reply at all. I called them more than 10 times but nobody answered me."

He said there had never been any anti-government protests in Qubair, but the nearby village of Maarzaf was strongly against the regime. He said Qubair and the surrounding villages were under a strict curfew and had been ordered to turn off all lights at night by the officer running a local checkpoint.

According to another opposition source, the Local Co-ordination Committee, shabiha – the militia men also blamed for the massacre in Houla – first shelled the agricultural village then went in and killed the residents.