Activists say Syrian security forces and snipers killed at least four people on Friday, as protesters launched anti-government protests across the country.
Activists say forces have fired shots at demonstrators in areas that include the flashpoint cities of Homs and Hama.
Meanwhile, the French news agency says a funeral for an army deserter evolved into an opposition rally in the northwestern Idlib province.
Opposition activists have urged protesters to rally for a "no fly" zone on Friday.
The activists made the call on social media sites, saying the flight restrictions are needed to help protect civilians from government forces.
Activists say at least eight people were killed in confrontations with Syrian security forces on Thursday. Also Thursday, thousands of supporters of President Bashar al-Assad rallied in the coastal city of Latakia.
For months, anti-government protesters have been calling for Mr. Assad's departure. The 22-member Arab League is trying to facilitate dialogue between government and the opposition's newly formed Syrian National Council.
The Syrian president has been facing growing international condemnation for his crackdown. The United Nations says the death toll has topped 3,000 during seven months of anti-government protests.
The Syrian government says armed gangs and "terrorists" are responsible for the majority of the violence.
Some information for this report was provided by AP, AFP and Reuters.