Peace envoy Kofi Annan deplored the killing of at least 108 people in the Syrian town of Houla as "an appalling crime" today and urged president Bashar al-Assad to prove he wants a peaceful resolution to the crisis racking his country.
Dr Assad's forces killed at least 41 people in an artillery assault on the city of Hama, activists said, shortly after the UN Security Council condemned Friday's massacre in nearby Houla.
With international criticism growing of Dr Assad's methods in trying to crush a 14-month-old uprising, now accompanied by a lightly armed insurgency, UN/Arab League envoy Mr Annan visited Damascus for talks on his faltering peace plan.
He explicitly urged the Syrian government to "take bold steps to signal that it is serious in its intention to resolve this crisis peacefully" before adding: "This message of peace is not only for the government, but for everyone with a gun."
Russia and China, which had previously vetoed UN resolutions condemning Dr Assad, both approved a non-binding text in New York yesterday that criticised the use of artillery and tank shells on homes in Houla - weapons the rebels do not have.
China said it was "deeply shocked by the large number of civilian casualties in Houla, and condemns in the strongest terms the cruel killings of ordinary citizens, especially women and children".
But by declining to blame the government alone, Russia and China kept their distance from Western and Sunni-led Arab countries that say Dr Assad must step down.
UN monitors say at least 108 people were killed in Houla, among them dozens of children.
But many of the victims were also hacked to death or shot at close range, as shown in graphic images distributed by activists, and UN monitors were unable to establish conclusively who killed these.
Russia and China have resisted joining Western and Arab League sanctions against Dr Assad. Both reaffirmed today that Mr Annan's plan, accepted by both sides in the conflict, was the only way forward and Russia suggested that the violence in Houla had been intended to sabotage his visit.
Chinese premier Wen Jiabao said support for the agreement, and a peaceful resolution, should be stepped up.
The deal calls for heavy weapons to be pulled out of towns and cities, followed by an end to fighting, and dialogue.
But the attack on Hama was a reminder that the plan, policed by just 300 monitors, has done little to stem the violence.
"The six-point plan has to be implemented comprehensively, and this is not happening," said Mr Annan, who was to meet foreign minister Walid al-Moualem today and Dr Assad tomorrow.
Opposition sources said Syrian tanks and armoured vehicles opened fire on several neighbourhoods of Hama on Sunday after attacks by rebel Free Syrian Army fighters on roadblocks and other positions manned by Dr Assad's forces.
The dead in the course of 24 hours included five women and eight children, the Hama Revolution Leadership Council said in a statement.
"Tank shelling brought down several buildings. Their inhabitants were pulled out from the rubble."
The report could not be independently verified.
UN secretary-general Ban Ki-Moon said in a letter to the security council that he hoped Syria would use Mr Annan's visit to "fundamentally change course and choose diplomacy over guns to ensure that the legitimate aspirations for freedom, dignity and prosperity of the Syrian people are met".
Mr Ban said a cluster of villages in the Houla area had been outside government control until Friday.
Houla is mostly populated by Sunni Muslims, while many of the surrounding villages are dominated by Alawites, the offshoot of Shia Islam that provides most of Dr Assad's ruling cadre.
A video distributed by activists showed an injured woman, who said she had survived the Houla massacre, blaming members of Dr Assad's shabbiha militia for the carnage.
"They entered our homes ... men wearing fatigues herding us like sheep in the room, and started spraying bullets at us," said the woman, lying next to another injured woman and near a baby with a chest wound.
"My father died and my brother, my mother's only son. Seven sisters were killed."
Syrian UN ambassador Bashar Ja'afari reiterated his government's assertion that the massacre was the work of "armed terrorist groups" - the Syrian government's term for the rebels.
He dismissed a "tsunami of lies" from the British, French and German envoys, who blamed the government for the massacre, among the worst carnage in an uprising that has cost more than 10,000 lives.
"We are dealing with a situation in which both sides evidently had a hand in the deaths of innocent people," Russian foreign minister Sergei Lavrov said at a news conference with visiting British foreign secretary William Hague.
French president Francois Hollande and British prime minister David Cameron discussed Syria by phone, condemning the "senseless murderous brutality of the Damascus regime" as a threat to regional security.
While both endorsed the Annan plan, they also called for an "orderly democratic transition" for Syria. Mr Hollande said France would call a meeting in Paris of the Friends of Syria - Western and Arab countries that want Dr Assad's rule to end.
Russia has accused the United States and Europe of pursuing Libya-style regime change in Syria, and is wary of endorsing any measures that could become a prelude to armed intervention.
Media reports have suggested that Washington is trying to enlist Russia for a plan of the kind that brought about a handover from Yemen's leader of three decades, Ali Abdullah Saleh, to an administration led by his own vice-president.
Russia has leverage over Syria through its security council veto and arms supply contracts, but does not wield the kind of influence that Saudi Arabia had over Mr Saleh as his main financier.
Russia also has a strong interest in keeping its Syrian naval base at Tartous, and may still see Dr Assad's survival as the best guarantee of this.
At his news conference with Hague, Mr Lavrov criticised those who argued that there could be no solution to Syria's crisis while Dr Assad remained in power.
Washington has explicitly said Dr Assad must step down.
Reuters