Syrians were called to the polls on Sunday to vote on a new constitution in the face of opposition calls for a boycott and in the thick of deadly violence that Washington said made the exercise "laughable."
The new text ends the legal basis for the five-decade stranglehold on power of the ruling Baath party but leaves huge powers in the hands of President Bashar al-Assad.
The opposition says the changes are entirely cosmetic and that only the departure from power of Assad will suffice after 11 months of repression by his security forces that human rights groups say have left more than 7,600 people dead.
On Saturday alone, 98 people were killed, 72 of them civilians, the Syrian Observatory for Human Rights said.
As polls opened at 7 am (0500 GMT), the Britain-based watchdog reported new violence in cities around the country.
In the central city of Homs -- under assault by regime forces for more than three weeks -- explosions were heard as shelling resumed of the rebel district of Baba Amro, dashing Red Cross hopes of a lull to allow the evacuation of two wounded Western journalists.
Explosions were also reported in the northeastern oil city of Deir Ezzor, the central city of Hama and the northwestern town of Idlib.
In Daraa province, south of Damascus, the cradle of the protests that erupted against Assad's regime in March last year, rebel troops clashed with soldiers in the town of Hirak. There was no immediate word on any casualties.
More than 14 million people over the age of 18 were eligible to vote in Sunday's referendum at 13,835 polling stations across the country.
Assad unveiled the proposed new national charter earlier this month, in the latest step in what he says is a cautious process of reform.
Dasmscus's allies, Beijing and Moscow, which have blocked action against the regime at the UN Security Council, have expressed support for the process.
"China hopes that national dialogue and reforms will move forward in Syria," Vice Foreign Minister Zhai Jun said after talks in Damascus earlier this month.
"We hope that the referendum on a new constitution as well as the forthcoming parliamentary elections pass off calmly," Zhai added.
Drawn up by a committee of 29 people appointed by the president, the new charter would drop the highly controversial Article 8 in the existing charter, which makes Assad's Baath party "the head of state and society."
Instead, the new political system would be based on "pluralism," although it would ban the formation of parties on religious lines.
Al-Baath, the ruling party's newspaper, said in an editorial this week that this "does not represent a loss for the party and just keeps up with political and social evolution."
While the new text drops all references to Syria being a socialist state, Article 60 maintains that half the deputies must be "workers and farmers."
Under the new charter, the president would maintain his grip on broad powers, as he would still name the prime minister and government and, in some cases, could veto legislation.
Another provision that has alerted secular groups and religious minorities is Article 3, which stipulates the president should be a Muslim, and that "Islamic jurisprudence shall be a major source of legislation."
Sunni Muslims account for 75 percent of Syria's population of 22 million, with the Alawite community that Assad hails from making up another 12 percent. But the country also has a sizeable Christian minority.
Article 88 states that the president can be elected for two seven-year terms, but Article 155 says these conditions only take effect after the next election for a head of state, set for 2014.
This means that Assad could theoretically stay at the helm for another 16 years.
And Syria specialist Thomas Pierret has said that regardless of the changes, the type of political system is of little relevance in a country "dominated by the intelligence service."
"Nothing indicates that this would change under the current regime," said Pierret, lecturer on Islam and Middle Eastern studies at the University of Edinburgh.