Syrians in government-controlled areas are heading to polling stations to elect a new 250-member parliament which is expected to serve as a rubber stamp for President Bashar Assad.

Around 3,500 government-approved candidates are competing after more than 7,000 others dropped out.

Parliamentary elections in Syria are held every four years, and Damascus says the vote is constitutional and separate from peace talks in Geneva aimed at ending the war.

But the opposition says the voting contributes to an unfavourable climate for negotiations amid fierce fighting that threatens an increasingly tenuous ceasefire engineered by the US and Russia.

Western leaders and members of the opposition have denounced the process as a sham and a provocation that undermines the Geneva peace talks.

The election, in which soldiers are being allowed to vote for the first time, will be conducted only in areas under government control.

Voting stations have been set up in 12 of Syria's 14 provinces. The northern province of Raqqa is controlled by the Islamic State group, and the north-western province of Idlib is controlled by its rival, the al Qaida-affiliated Nusra Front, as well as other insurgent factions. The government has no presence in either province.

The results are expected on Thursday.