"More than 30 civilians have been killed over the past 24 hours in Homs in clashes that broke out late on Saturday between the opposition and supporters of the regime," said Rami Abdel Rahman of the London-based Syrian Observatory for Human Rights.

He said the clashes came after three regime supporters kidnapped last week were killed and their dismembered bodies were returned to their relatives on Saturday.

"These clashes are a dangerous development that undermines the revolution and serves the interests of its enemies who want it to turn into a civil war," he added.

"The two sides started out beating each other with sticks, but then firearms were used," Abdel Rahman said. A large number of the dead were killed by gunmen lying in ambush, he added.

The clashes began in the city's Hadara district before spreading to several other areas, and security forces did not intervene, Abdel Rahman said.

"Their duty is to maintain national security and protect citizens, not stand idly by when faced with clashes, as this can encourage even more violence," he charged.

Copyright AFP (Agence France-Presse), 2011