The UN chief has condemned a new reported massacre in Syria as "an unspeakable barbarity” and called again on the country’s president, Bashar al-Assad, to implement immediately the six-point peace plan of international mediator Kofi Annan.Ban Ki-moon, speaking on Thursday at the start of a special UN General Assembly session on the Syrian crisis, also revealed that UN monitors seeking to reach the site of the apparent massacre of Syrian villagers by forces loyal to Assad were shot at with small arms.Earlier, Norwegian General Robert Mood said in a statement that the UN ceasefire observers - who are authorised by the Syrian government - were being stopped and in some cases turned back at Syrian army checkpoints.He said some UN patrols were also being stopped by civilians, and that some residents in the area of the alleged massacre said the observers’ would be at risk if they entered.The UN mission dispatched observers after receiving reports of a mass killing in al-Qubayr, a small village. Opposition activists said that pro-government armed groups backed by security forces killed scores of people there.Both the Syria’s Local Co-ordination Committees, an activist network, and the UK-based Syrian Observatory for Human Rights (SOHR) said that more than 86 people had died. Syria’s government denied any role in the killings."What a few media have reported on what happened in al-Qubayr, in the Hama region, is completely false,” the government said in a statement on official television."A terrorist group committed a heinous crime in the Hama region which claimed nine victims. The reports by the media are contributing to spilling the blood of Syrians,” the statement said.‘Atmosphere of terror’Mousab al-Hamadee, an activist in Hama, told Al Jazeera that the attack bore similarities to last month’s massacre in Houla, and said the government was seeking to create an "atmosphere of terror and intimidation”.He said the Syrian army had prepared the way by shelling the area before pro-government gangs descended on the village."Most of victims were burnt in their houses, many of them were slaughtered by knives in a very ugly way,” he said, adding that women and children were among the dead. He also criticised the role of the UN monitoring mission."Unfortunately they do nothing to protect us, they just come the next day after the massacres to film the corpses and see how we bury our victims … They are just watching us die,” he said.