Egyptians stood in line to vote on Saturday on a constitution promoted by its Islamist backers as the way out of a prolonged political crisis and rejected by opponents as a recipe for further divisions in the Arab world's biggest nation.
Soldiers joined police to secure the referendum after deadly protests during the build up. Street brawls erupted again on Friday in Alexandria, Egypt's second city, but voting proceeded quietly there, with no reports of violence elsewhere.
President Mohamed Mursi provoked angry demonstrations when he issued a decree last month expanding his powers and then fast-tracked the draft constitution through an assembly dominated by his Muslim Brotherhood group and its allies. At least eight people were killed in clashes last week outside the presidential palace.
The liberal, secular and Christian opposition says the constitution is too Islamist and tramples on minority rights. Mursi's supporters say the charter is needed if progress is to be made towards democracy nearly two years after the fall of military-backed strongman Hosni Mubarak.
"The sheikhs (preachers) told us to say 'yes' and I have read the constitution and I liked it," said Adel Imam, a 53-year-old queuing to vote in a Cairo suburb. "The president's authorities are less than before. He can't be a dictator."
Opposition politician and Nobel Peace Prize laureate Mohamed ElBaradei wrote on Twitter: "Adoption of (a) divisive draft constitution that violates universal values and freedoms is a sure way to institutionalise instability and turmoil."
Official results will not be announced until after a second round of voting next Saturday. But partial results and unofficial tallies are likely to emerge soon after the first round, giving an idea of the overall trend.
In order to pass, the constitution must be approved by more than 50 percent of voters who cast ballots. A little more than half of Egypt's electorate of 51 million are eligible to vote in the first round in Cairo and other cities.
Christians, making up about 10 percent of Egypt's 83 million people and who have long grumbled of discrimination, were among those waiting at a polling station in Alexandria to oppose the basic law. They fear Islamists, long repressed by Mubarak, will restrict social and other freedoms.
"I voted 'no' to the constitution out of patriotic duty," Michael Nour, a 45-year-old Christian teacher in Alexandria. "The constitution does not represent all Egyptians," he said.
Islamists are counting on their disciplined ranks of supporters and the many Egyptians who may fall into line in a desperate bid to end turmoil that has hammered the economy and sent Egypt's pound to eight-year lows against the dollar.
"I voted 'yes' for stability," said shopkeeper Ahmed Abou Rabu, 39. "I cannot say all the articles of the constitution are perfect but I am voting for a way forward. I don't want Egyptians to go in circles, for ever lost in this transition."
Mursi was among the early voters after polls opened at 8 a.m. (0600 GMT). He was shown on television casting his ballot shielded by a screen and then dipping his finger in ink - a measure to prevent people voting twice.
One senior official in the committee overseeing the referendum said Saturday's vote could extend to Sunday if crowds were too heavy to allow everyone cast ballots in one day. Voting for Egyptians abroad that began on Wednesday has been extended to Monday, the state news agency reported.
After weeks of turbulence, there has been limited public campaigning. Opposition politicians and parties, beaten in two elections since Mubarak's overthrow, only announced on Wednesday they backed a "no" vote instead of a boycott.
Flag-waving Islamists gathered peacefully at one of the main mosques on Friday, some shouting "Islam, Islam" and "We've come here to say 'yes' to the constitution".
Opposition supporters assembled outside the presidential palace, where there has been a sit-in for days. The walls of the palace, ringed by tanks, are scrawled with anti-Mursi graffiti.
The referendum will be held on two days covering different regions, with the second round on Dec. 22, because there are not enough judges willing to monitor all polling stations after some in the judiciary said they would boycott the vote.
Egyptians are being asked to accept or reject a constitution that must be in place before a parliamentary election can be held next year to replace an Islamist-led parliament dissolved this year. Many hope this will lead Egypt towards stability.
If the constitution is voted down, a new assembly will have to be formed to draft a revised version, a process that could take up to nine months.
The army has deployed about 120,000 troops and 6,000 tanks and armoured vehicles to protect polling stations and other government buildings. While the military backed Mubarak and his predecessors, it has not intervened in the present crisis.