BEIRUT: Unarmed United Nations monitors came under fire Thursday as they tried to reach the scene of the latest mass killing in Syria, UN Secretary-General Ban Ki-moon said.

Activists accused government forces of killing nearly 80 people, including women and children who were shot, hacked to death and burned in their homes.

The reports came just weeks after more than 100 people were killed in one day in a cluster of villages known as Houla in central Homs province, many of them children and women gunned down in their homes.

UN investigators blamed pro-government gunmen for at least some of the killings, but the Syrian regime denied responsibility and blamed rebels for the deaths.

The Houla massacre brought international outrage and a coordinated expulsion of Syrian diplomats from world capitals.

Ban told the UN General Assembly that the monitors ''were shot at with small arms'' as they tried to reach Mazraat al-Qubair, a farming area in the central Hama province. The group was denied access. By nightfall, the UN observers had not managed to visit the village, said spokesman Kieran Dwyer.

No observers were injured and it was not clear who was behind the shooting, the UN said.

International envoy Kofi Annan, who tried to broker a plan to end the crisis, offered a grim assessment of the coming days and weeks in Syria.

''If things do not change, the future is likely to be one of brutal repression, massacres, sectarian violence, and even all-out civil war,'' Annan told the General Assembly. ''All Syrians will lose.''

Syria denied that its forces committed the mass killing in Mazraat al-Qubair on Wednesday, dismissing the claims as ''absolutely baseless.''

The regime blamed the violence on terrorists who are trying to provoke foreign military intervention to topple Assad. A fuller picture is unlikely to emerge before UN observers can enter the rural village.

A resident of Mazraat al-Qubair said troops shelled the area for five hours Wednesday before government-aligned militiamen known as shabiha entered the area, ''killing and hacking everyone they could find.''

Leith Al-Hamwy told The Associated Press by telephone that he survived by hiding in an olive grove about 800 meters (yards) from the farms as the killings were taking place. But he said his mother and six siblings, the youngest 10-year-old twins, did not.

''When I came out of hiding and went inside the houses, I saw bodies everywhere. Entire families either shot or killed with sharp sticks and knives,'' he said. Al-Hamwy said the gunmen set his family home on fire and his family burned to death. Around 80 people in total died, he said, many of them children, and 18 homes were either destroyed by the shelling or burned down.

Gen. Robert Mood, the head of the observers mission in Syria, said UN patrols headed to the village of were stopped at Syrian army checkpoints and in some cases turned back. He said some patrols were also stopped by civilians and added they had received information from residents of the area that the safety of observers was at risk if they entered the village.

US Secretary of State Hillary Rodham Clinton condemned the Syrian government.

''The regime-sponsored violence that we witnessed again in Hama yesterday is simply unconscionable,'' she said in Turkey. ''Assad has doubled down on his brutality and duplicity, and Syria will not, cannot be peaceful, stable or certainly democratic until Assad goes.''

The exact death toll and circumstances of the killings overnight in Mazraat al-Qubair were impossible to confirm. The violence is bound to reinforce the growing belief that a peace plan brokered by Kofi Annan is unraveling as the country spirals toward civil war.

Both Homs and Hama have been centers of opposition to Assad's rule during the 15-month uprising.

The Britain-based Observatory for Human Rights said it had compiled the names of at least 49 people who had died in the massacre. But Rami Abdul-Rahman, director of the group which relies on a network of activists on the ground, said the circumstances of the killings were still unclear and called on UN observers to visit the area immediately.