By Tamim Elyan and Marwa Awad
CAIRO/ALEXANDRIA, Dec 15 (Reuters) - Egyptians voted 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.
Queues formed outside polling stations in Cairo and other cities and soldiers joined police to secure the referendum process after deadly protests during the build up. Street brawls again erupted on Friday in Alexandria, Egypt's second city.
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 president's 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 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."
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 Alexandria on Friday, tensions boiled over into a street brawl between rival factions armed with clubs, knives and swords. Several cars were set on fire and a Muslim preacher who had urged people to vote "yes" to the constitution was trapped inside his mosque by angry opposition supporters.
Christians, making up about 10 percent of Egypt's 83 million people and who have long grumbled of discrimination, were among those queuing at a polling station in the port city 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. The constitution does not represent all Egyptians," said Michael Nour, a 45-year-old Christian school teacher in Alexandria.
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.
Polling stations close at 7 p.m. (1700 GMT), but the deadline could be extended depending on turnout.
After weeks of turbulence, there has been limited public campaigning. Disparate opposition politicians and parties, beaten in two elections since Mubarak's overthrow, only announced on Wednesday they backed a "no" vote over 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.
Just over half of Egypt's electorate of 51 million will vote in the first round in Cairo and other cities.
To provide security for the vote, 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 on either side in the present crisis.
The charter has been criticised by some overseas bodies.
The International Council of Jurists, a Geneva-based human rights group, said it falls short of international standards on the accountability of the armed forces, the independence of the judiciary, and recognition of human rights.
United Nations human rights experts said the draft should be reviewed to ensure Egypt meets its obligations under international law on equality and women's rights.