Ban Ki-moon increases pressure on Syria
UN Secretary General Ban Ki-moon has expressed deep frustration with the violence in Syria, two days after reports emerged of another massacre.
Mr Ban said there was little evidence that Syria's government was complying with envoy Kofi Annan's peace plan.
Activists say government-backed militias killed 78 people in Qubair village on Wednesday. The government said terrorists killed nine people.
UN observers are expected to try to reach the village later.
They were shot at and forced to turn back while trying to reach Qubair on Thursday.
The BBC's Jim Muir in neighbouring Lebanon says the need for the observers to find out what actually happened at Qubair is made all the more acute by the fact that there are two completely contradictory accounts of what happened.
Syrian state TV is repeatedly showing pictures of dead children, accusing the opposition of staging the killings of nine people to spark international intervention.
But opposition activists are equally adamant that a much larger massacre was perpetrated by militias known as shabiha.
The activists say government forces removed many of the bodies while the UN observers were trying to get to the village.
Western media organisations are restricted in Syria, making it difficult to verify the claims of either side.
"The danger of a full-scale war is imminent and real," Mr Ban told a joint news conference with Mr Annan and Arab League Secretary General Nabil al-Arabi.
"Reports of yet another massacre in Qubair underscore the horrifying reality on the ground," he said.
"How many more times have we to condemn them, and how many ways must we say that we are outraged? The Syrian people are bleeding."
And while reiterating that Mr Annan's six-point peace plan remained "at the centre of our focus", he said urgent talks were needed to discuss how to proceed further.
The US is demanding decisive action, but Russia and China are both opposing any outside intervention.
At the news conference, Mr Annan also confirmed that discussions were taking place on forming a contact group of key nations on Syria.
He said that the group would exert more pressure on both the government of President Bashar al-Assad and the opposition to comply with the peace plan.
But the possible participation of Iran in the group has already proved controversial.
Although Mr Annan expressed hopes that Iran would be part of the solution, the US and UK earlier ruled out Tehran's participation.
On Friday, activists said government forces had resumed shelling the city of Homs, where they were engaged in a battle to try to retake districts controlled by rebels.
The UN says at least 9,000 people have died since pro-democracy protests began in March 2011. In April, the Syrian government reported that 6,143 Syrian citizens had been killed by "terrorist groups".
The UN has 297 unarmed observers in Syria to verify the implementation of Mr Annan's six-point plan. It includes a ceasefire, which was supposed to have taken effect in mid-April.
However, deaths are reported every day, with about 200 people said to have died on Wednesday and Thursday this week.