Amnesty International on Thursday accused Syria of committing crimes against humanity to punish communities supporting rebels, as monitors reported a spate of car bombs and clashes which killed dozens more people.
The London-based rights group called for an international response after claiming it had fresh evidence that victims, including children, had been dragged from their homes and shot dead by soldiers, who in some cases then set the remains on fire.
"This disturbing new evidence of an organised pattern of grave abuses highlights the pressing need for decisive international action," said Amnesty's Donatella Rovera on the release of the 70-page report entitled Deadly Reprisals.
The advocacy group interviewed people in 23 towns and villages across Syria and concluded that government forces and militias were guilty of "grave human rights violations and serious violations of international humanitarian law amounting to crimes against humanity and war crimes."
The allegations came as the Syrian Observatory for Human Rights reported that more than 14,400 people have been killed in Syria in the 15-month revolt against President Bashar al-Assad's regime, including 2,302 in the past month alone.
"There have been 14,476 people killed since March 2011, among them 10,117 civilians, 3,552 soldiers and 807 army defectors," Rami Abdel Rahman, head of the Observatory, told AFP.
Early Thursday, a suicide bomber detonated an explosives-packed vehicle in a Damascus suburb, wounding 14 people and damaging one of Shiite Islam's holiest shrines, state media and witnesses reported.
The official news agency SANA reported that the bomb exploded in a garage some 50 metres (yards) from the Sayyida Zeinab shrine and that "the terrorist who carried out the operation was killed."
An AFP photographer at the site said the shrine's windows were shattered by the force of the blast, while parts of the mosaics on the shrine's two minarets broke off.
The Sayyida Zeinab mausoleum houses the tomb of the prophet Mohammed's granddaughter and the site is extremely popular with Shiite pilgrims, especially from Iran, a staunch ally of the regime in Damascus.
Also early Thursday, car bomb in Idlib city in northwestern Syria targeted a military checkpoint, the Syrian Observatory for Human Rights said, adding that a number of soldiers were killed or wounded in the blast.
No further details were immediately available.
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The Observatory said meanwhile that clashes between regime troops and rebels erupted early morning in the central city of Homs, where four people were killed before dawn, including three civilians and a rebel fighter.
Ahmed Bahbouh, the head of the rebel military office in Rastan and a leading dissident figure, was killed in violent clashes with government forces in Homs province, the watchdog added.
And a civilian was killed in crossfire as rebel fighters and government troops clashed at the entrances of the rebel-held town, which the regime has been trying to overrun for months.
In the southern city of Daraa, five people were killed before dawn, including four in the neighbourhood of Tareek al-Sad which was heavily shelled by regime troops, the Observatory said.
On the diplomatic front, a mistranslation Wednesday of remarks made in Tehran by Russian Foreign Minister Sergei Lavrov threatened to further heat a diplomatic row between Russia and the United States.
Lavrov was quoted in Iranian media as accusing the US of supplying weapons to rebels who are battling the regime.
Russia's foreign ministry later insisted that Lavrov had been speaking about US weapons supplies "in the region."
Washington and Moscow are already at swords drawn after US Secretary of State Hillary Clinton said on Tuesday she had information that Russia was sending attack helicopters to Syria, "which will escalate the conflict quite dramatically."
Lavrov responded to her comments during a brief visit to Iran by saying that Russia was supplying "anti-air defence systems" to Damascus in a deal that "in no way violates international laws."
Clinton later Wednesday stood firm on her call for an end to arms shipments, at a news conference in Washington.
"I was very clear yesterday about our concerns regarding the continuing military relationship between Moscow and the Assad regime," Clinton said.
"We have repeatedly urged the Russian government to cut these military ties completely and to suspend all further support and deliveries," she added.
China meanwhile said on Thursday it disapproved of "one-sided" sanctions and pressure on Syria after France raised the prospect of a new raft of punitive measures against Assad's regime.