Egyptians have begun voting in the second and final phase of the country's bitterly divisive constitutional referendum which has sparked weeks of unrest.

But with clashes continuing between supporters and opponents of the Islamist president, Mohammed Morsi, on Friday in Alexandria, there is little sign that the result of the vote will end Egypt's political crisis.

Saturday's vote is taking place in 17 of Egypt's 27 provinces with about 25 million eligible voters.

Around 250,000 security personnel have been deployed nationwide to try to keep order during the vote.

Unofficial results for the first phase of the referendum on 15 December showed about 56% approval to 43% rejection for the draft constitution on a low turnout of 32%. The prospects of a win for the no vote are poorer in Saturday's ballots.

Opponents of Morsi, including liberals, leftists and secular Egyptians, say the draft favours the Islamists, including the president's Muslim Brotherhood, and will create a new Mubarak-style autocracy in betrayal of the revolution that overthrew the former dictator last year.

The president's supporters say the new constitution will secure democracy and accuse the opposition of trying to use the streets to overturn their victories at the ballot box over the past two years.

"I came early to make sure my 'no' is among the first of millions today," oil company manager Mahmoud Abdel-Aziz told Associated Press as he waited outside a polling station in the Dokki district of Giza. "I am here to say no to Morsi and his Muslim Brotherhood," he added.

Another Giza voter, accountant and mother of three Sahar Mohamed Zakaria, said: "I'm voting yes for stability."

Hanaa Zakim, a Christian from Fayoum province, where Islamist groups have traditionally had strong support, said she was also voting yes for stability and an end to the country's deepening economic problems. Most Christians are seen to oppose the draft.

She said: "I have a son who didn't get paid for the past six months. We have been in this crisis for so long and we are fed up."

If the constitution is approved, Morsi will call for the election of parliament's lower chamber to be held within two months while giving the upper chamber legislative powers until then.

The upper chamber, known as the Shura council, was elected by less than 10% of registered voters. It is dominated by Islamists.