As voting began, security forces battled pro-opposition army defectors in fierce clashes that are overshadowing the peaceful street protests that began the uprising against Assad nine months ago with fears that Syria is drifting into civil war.

Monday also saw the second day of the opposition's "Strike for Dignity", widely supported in protest strongholds around the country and which activists say security forces have tried to break by force and threats.

Opposition activists said security forces were forcing people to go to the polls in Idlib province.

Voters were heading to the polls in the morning, state media said, but it was unclear if there would be a big turnout in cities such as Homs, Hama and Deraa, where residents have been too scared by violence to leave their homes in recent days.

Assad's government said the polls are part of a process of reform leading to a parliamentary election next year and constitutional reform. But critics say the polls have little significance as municipal officials have little power in a centralized autocratic government.

Assad has said reforms cannot be rushed in Syria, where his Baath Party has held a monopoly on power.

Activists said fighting erupted in the southern town of Dael when security forces moved in to break up the strike. The Syrian Observatory for Human Rights also reported clashes between deserters and the army in parts of northern Idlib province, where at least three civilians were shot dead by the security forces.

Though the strike has found support in protest strongholds it has not taken hold in central parts of the capital Damascus or the business hub of Aleppo.

Activists want the strike to take hold, boosting the number of Syrians prepared to oppose the government through civil disobedience rather than armed confrontation, which they fear could lead to civil war and play into the hands of Assad.

"The cost will be more human lives I am afraid. But it is less costly than an armed uprising and the regime dragging the country into a Libya-type scenario," said Rima Fleihan, a member of the foreign-based opposition Syrian National Council.