Polling stations opened at 07:00 a.m. local time (0400 GMT), with the official SANA news agency saying they will remain open until 7 p.m. (1800 GMT).
Voting, it said, could be extended for five hours by the Higher Judicial Committee for Elections depending on the turnout which it reported high at the opening hours.
More than 7,300 polling stations have been set up across the government-held regions in the country. Syrian voters are electing members of the 250-seat parliament out of some 3,500 candidates.
A number of opposition parties are running in the race, but the ruling Ba'ath party is expected to prevail. Armed opposition groups have boycotted the vote and called it illegitimate.
A smiling President Bashar al-Assad and his wife Asma cast their ballots in Damascus and spoke to voters at the polling station.
Walls across the capital Damascus were covered with campaign posters. From the top of one of the city's tallest buildings a banner proclaimed: "The elections of resistance."
"I voted because this election will decide the country's future. I hope that the winners will be true to the nation even before being true to the voters," Yamin al-Homsi, a 37-year old who voted in Damascus, told AFP.
Samer Issa, a taxi driver, said he had "fulfilled his national duty" by casting his vote.
"Now, it's up to the winners to fulfill their promises," the 58-year-old added, according to the French news agency.
The polls coincide with the beginning of a second round of UN-brokered indirect talks between the Syrian government and the opposition in Geneva, with the future of President Assad being a key sticking point.
The foreign-backed Syrian opposition says Assad must step down before a transitional government can be established.
Foreign Minister Walid al-Muallem has said the fate of President Assad remains a "red line" for the Syrian government in the Geneva talks.
The last round of the UN-backed peace talks for Syria came to a halt on March 24 over disagreements on the role of Assad in Syria’s future.
UN Syria envoy Staffan de Mistura will try again to reach a consensus at the talks starting Wednesday in Geneva on ending the war.
The negotiations come at a tense time with a surge in violence in recent days threatening a fragile six-week ceasefire.
Syria has been gripped by foreign-backed militancy since March 2011. According to the so-called Syrian Observatory for Human Rights, at least 270,000 people have been killed in the conflict. Some reports, however, put the death toll at as high as 470,000.
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