The Syrian regime on Friday accused rebels of carrying out a "brutal massacre" of 25 of its supporters, as neighbouring Turkey held emergency talks after a Turkish military plane went missing near Syria.
Monitors said regime forces fired on demonstrators in second-largest city Aleppo killing at least eight people while another was killed in the province of the same name.
UN-Arab League envoy Kofi Annan, meanwhile, urged the international community to raise the level of pressure on both sides in the conflict which monitors say has cost more than 15,000 lives since March 2011.
"It's time for countries of influence to raise the level of pressure on the parties on the ground and to persuade them to stop the killing and start the talking," he told a press conference in Geneva.
In neighbouring Turkey, the plane incident triggered an emergency summit of military, intelligence and government officials.
NTV private news channel reported citing unnamed military sources that the plane crashed in Syrian territorial waters, but there was no violation of the Syrian border.
Prime Minister Recep Tayyip Erdogan, quoted by local media, said the two pilots were alive. Syrian and Turkish coastal guards were collaborating to reach the plane wreck, NTV said earlier.
The Syrian Observatory for Human Rights gave a higher toll for the pro-regime losses in the latest reported massacre, saying at least 26 government supporters -- most of them members of the feared shabiha militia -- had been killed.
The Britain-based watchdog also reported that government forces opened fire on demonstrators in Aleppo province killing nine, as activists called nationwide protests.
In the capital, troops fired on demonstrators in the upscale district of Mazzeh, the watchdog said, without giving any immediate word on casualties.
Protesters in other areas of Damascus and its suburbs were also fired on, the Observatory said, adding that two children were shot dead in two different areas of Damascus province, although not at demonstrations.
In Syria's third largest city Homs, residents held a small protest despite a renewed bombardment by government forces of rebel-held neighbourhoods, activists said.
It came after at least 168 were killed in violence across Syria on Thursday, the highest single-day death toll since a UN-backed ceasefire was supposed to take effect on April 12, the Observatory said.
In the reported massacre, "armed terrorist groups... kidnapped a number of citizens in Daret Azzeh area in the countryside of Aleppo, according to official sources in the province," the state SANA news agency said.
"The terrorist groups... committed a brutal massacre against the citizens... through shooting them dead and then mutilating their bodies." it added.
"Initial information indicates that more than 25 of the kidnapped citizens were killed... with the fate of the rest of the kidnapped people still unknown."
Amateur video posted on YouTube and distributed by the Observatory showed piles of mangled bodies of young men, their clothing soaked in blood. At least two of the bodies in the footage were wearing fatigues.
"These are shabiha of (President) Bashar al-Assad's regime," the narrator said, without identifying himself.
The Observatory said a total of at least 52 people were killed in violence across the country on Friday.
The UN Office for the Coordination of Humanitarian Affairs (OCHA), meanwhile, said up to 1.5 million Syrians now need humanitarian aid, up from the one million estimated at the end of March.
"The humanitarian situation in Syria continues to deteriorate," said the latest OCHA bulletin.
"We called on them (the Syrian regime) to back up their declarations about readiness to implement the Kofi Annan plan with deeds," Lavrov told state television after the meeting in Russia's second city of Saint Petersburg.
"They have already done a lot but they can and must do much more."
Lavrov said Muallem had promised him in the name of Assad that the government was ready for a "synchronised" withdrawal of troops from Syrian towns as long as the rebel opposition did the same.
"The minister assured me of this today," he said.
Source: AFP Global Edition