Dozens of bodies have been dumped in the streets of a Syrian city at the heart of the country's nine-month-old uprising, a grim sign that sectarian bloodshed is escalating.
The discovery in the streets of Homs came as the United States stepped up pressure on the regime of President Bashar Assad to end its crackdown on the anti-government protests.
US Secretary of State Hillary Clinton met in Geneva with Syrian opposition figures and Washington said it was sending its ambassador back to Damascus.
Up to 50 people were killed in Homs on Monday, but details about what happened in Syria's third-largest city only came to light today with reports of retaliatory attacks pitting members of the Alawite sect against Sunnis.
The sectarian violence is a dire development in Syria, and one that opposition members say plays directly into the regime's hands.
Since the uprising began, Mr Assad portrayed himself as the lone force who can ward off the radicalism and sectarianism that have bedevilled neighbours in Iraq and Lebanon.
Opposition figures have accused Mr Assad's minority Alawite regime of trying to stir up trouble with the Sunni majority to blunt enthusiasm for the uprising.
"It was an insane escalation," activist Mohamed Saleh said by telephone from Homs. "There were kidnappings and killings in a mad way. People are afraid to go out of their homes."
Thirty-four of the dead were shot execution-style, their bodies dumped in a public square, according to Mr Saleh and others who monitor the violence, including the British-based Syrian Observatory for Human Rights.
A Homs government official confirmed only that 43 bodies were found on Monday in Homs. With 4,000 people dead across Syria in the uprising, the conflict is no longer just a matter of government forces firing on peaceful protesters looking to topple Mr Assad's autocratic regime.