Seventeen people, including 10 women, were reportedly killed overnight by shelling in the Syrian town of Deraa, where the uprising against president Bashar al-Assad began 15 months ago.
Fighting was also reported in Homs and Damascus, killing a total of 44 civilians yesterday, the Syrian Observatory for Human Rights said, showing neither side was respecting a UN-backed ceasefire, the failure of which has left outside powers divided on what to do next.
Two massacres of civilians in the last two weeks have added urgency to talks between foreign powers on what to do since the ceasefire, supposed to take effect on April 12th, has failed to stop the violence.
Russia said today it would not oppose the departure of Dr Assad if such a move is a result of a dialogue between Syrians themselves and is not enforced through external pressure. "If the Syrians agree between each other, we will only be happy to support such a solution," foreign minister Sergei Lavrov told reporters. "But we believe it is unacceptable to impose the conditions for such a dialogue from outside."
Washington - which is in frequent, high-level contact with Moscow over the Syria crisis - opposes Russia's view that Assad's ally Iran should attend any such meeting.
Russia has used its UN Security Council veto to shield Dr Assad from co-ordinated condemnation and sanctions, concerned about what it sees as the West's desire for Libya-style regime change and keen to maintain its firmest Middle East foothold.
US secretary of state Hillary Clinton said on Wednesday it was "hard to imagine inviting a country that is stage-managing the Assad regime's assault on its people."
Washington accuses Iran of aiding the Syrian government and pro-Assad militia in putting down the uprising, something Tehran denies.
Underlining the sectarian nature of the conflict, rebels holding 11 Lebanese Shia Muslim pilgrims hostage said they would release the men when their country had established a new "civil state", a video obtained by al-Jazeera television showed.
"The guests will be released by the Syrian civil state when their case is reviewed by a new democratic parliament," the rebels said in a written statement on the video in which the hostages appeared, apparently in good health .
But the statement left room for negotiations, saying: "Given the current conditions it may be possible to negotiate their release with neighbouring countries."
The hostages were on a bus that was stopped by gunmen as it crossed into northern Syria from Turkey on its way home from a pilgrimage to Iran.
The revolt has been led mostly by Syria's Sunni Muslim majority. Many say their interests have been crushed under Dr Assad who is from a minority Alawite sect considered an offshoot of Shia Islam.
United Nations monitors are still working to understand what happened in the hamlet of Mazraat al-Qubeir, where opposition activists say at least 78 people were massacred on Wednesday. The monitors saw empty homes covered in blood and smelled burnt flesh when they visited yesterday.
Armoured-vehicle tracks were visible in the vicinity and some homes were damaged by rockets from armoured vehicles. Only the Syrian army has armoured vehicles and heavy weapons.
The incident happened two weeks after a massacre in the town of Houla, killing at least 108 men, women and children, which the United Nations said seemed to be the work of Syrian government forces and allied militias.
The UN said several weeks ago that at least 9,000 people have been killed since the crisis began while Syrian activists say the violence has claimed the lives of more than 13,000 people.
Agencies