Many Syrian civilians are fleeing their homes to escape escalating conflict between government forces and rebels, the Red Cross said yesterday, while major powers seemed unable to craft an alternative to envoy Kofi Annan's failing peace plan.

UN monitors meanwhile reached the scene of a reported massacre that has underlined how little outside powers have been able to do to halt 15 months of carnage in Syria.

A day after one team was shot at and turned back, another group of UN monitors entered the hamlet of Mazraat al-Qubeir, where opposition activists say 78 people were shot, stabbed or burned alive on Wednesday.

A correspondent for the BBC, Paul Danahar, said he was with the UN team and described traces of a violent scene in the village using his Twitter account.

"In front of me there is a piece of brain, in the corner there is a mass of congealed blood ... The largest of the two houses on the hilltop in Qubeir has been gutted by fire. The stench of flesh is still strong," he wrote. "Inside the buildings are gutted. The UN have not found any people yet."

Some 300 UN observers are in Syria to monitor a "truce" between President Bashar al-Assad's forces and rebels, which Annan declared on April 12 but was never implemented. Now reduced to observing the violence, they have already verified one massacre in Houla, a town where 108 men, women and children were slain on May 25.

The Syrian authorities have condemned the killings in Houla and Mazraat al-Qubeir, blaming them on "terrorists".

More and more civilians are fleeing their homes to escape fighting, while sick or wounded people are finding it hard to reach medical services or buy food, said a spokesman for the Red Cross in Geneva.

UN Secretary-General Ban Ki-moon told the General Assembly on Thursday a civil war was imminent and that "terrorists are exploiting the chaos" in Syria, adding that hopes of implementing Mr Annan's plan were fading.

Mr Annan – Mr Ban's predecessor as UN secretary-general, warned the UN Security Council the crisis could soon fly out of control. He called for "substantial pressure" on Damascus to stop the violence.

Given the failure of the peace plan, there is little to check the violence, now often sectarian in nature, pitting Mr Assad's minority Alawites against the Sunni Muslim majority.

Protests erupted across the country yesterday, a day after 31 people were killed and the state news agency announced the burials of 29 soldiers and security men killed by rebels. A car bomb aimed at a bus carrying security men exploded in a Damascus suburb, killing at least two, the Syrian Observatory for Human Rights watchdog said.

Another car bomb hit a police branch in the city of Idlib, killing at least five people, it claimed.

Government forces shelled and then tried to storm the rebel-held district of Khalidiya in the central city of Homs, the heart of the revolt against Mr Assad, the UK-based Observatory said.

Activists said the shelling of Khalidiya was the fiercest yet to hit Homs, with up to 10 rockets a minute striking the neighbourhood. Videos uploaded to the internet showed columns of grey smoke rising into the air. No death toll was available, but the Observatory said most residents had fled during previous bombardments.

In Deraa, southern birthplace of the uprising, government forces pounded rebel hideouts in the rugged Luja area.