By Edmund Blair
CAIRO (Reuters) - An Egyptian constitution drafted by Islamists is expected to be approved in a referendum on Saturday after the charter, which opponents say will create deeper turmoil, won approval in a first wave of voting a week ago.
The opposition have already cried foul, saying a litany of abuses means last Saturday's ballot, involving about half the electorate, should be re-run. But the committee overseeing the two-stage vote said their investigations showed no major irregularities that would invalidate the process.
Islamist supporters of President Mohamed Mursi, who was elected in June, say the constitution is vital to moving Egypt towards democracy two years after Hosni Mubarak was overthrown in a popular uprising. They say it will help restore the stability needed to fix an economy that is on the ropes.
If the basic law is passed, a parliamentary election will be held in about two months.
Polling stations open at 8 a.m. (0600 GMT) and close at 7 p.m. (1700 GMT) though voting is likely to be extended as it was last week. Unofficial tallies are likely to emerge within hours, but the referendum committee may not declare an official result for the two rounds until Monday, after hearing appeals.
The opposition says the constitution is divisive and accuses Mursi of pushing through a document that leans towards his Islamist allies and ignores the rights of Christians, who make up about 10 percent of the population, as well as women.
"I see more unrest," said Ahmed Said, head of the liberal Free Egyptians Party and a member of the National Salvation Front, an opposition coalition brought to together after Mursi expanded his powers on November 22 and then pushed the constitution to a vote.
Citing what he said were "serious violations" on the first day of voting on December 15, he said anger against Mursi and his Islamist allies was growing: "People are not going to accept the way they are dealing with the situation."
Deadly violence marred the build up to the vote. At least eight people were killed in protests outside the presidential palace in Cairo earlier this month.
Islamists and rivals clashed again on Friday in the second biggest city of Alexandria, hurling stones at each other outside a major mosque and in nearby streets. Two buses were torched while police tried to separate the rivals by firing tear gas.
Unofficial tallies in state media said 57 percent of those who voted last week backed the constitution. Analysts said the second day's ballot was likely to deliver another Yes vote, possibly by a bigger margin, because it would be held in several rural and other areas seen as having more Islamist sympathizers.
Opponents also say Saturday's vote could well go in Mursi's favor, but say this will be due to further abuses. Islamists dismiss such charges and say they are confident of a bigger win.
Mohamed Beltagy, a senior official in the Muslim Brotherhood, the group that propelled Mursi to elected office, said the constitution was crucial to holding a parliamentary election and completing a process of setting up essential state institutions.
"What is the catastrophe of this constitution?" he asked the assembly which drafted the document, during a sitting on Friday that was called to challenge opposition criticism of the text.
Opponents, who had earlier quit the drafting assembly saying their voices were not heard, were invited but stayed away.
There are 51 million eligible voters in Egypt, with roughly half allowed to vote in each round. The vote was staggered after many judges refused to supervise the vote, meaning there were not enough to hold the referendum on a single day nationwide.
The first round was won by a slim enough margin to buttress opposition arguments that the text was divisive. Opponents who include liberals, leftists, Christians and more moderate-minded Muslims accuse Islamists of using religion to sway voters.
"The problem is not whether the majority approves, it is that they rallied the people in the name of the religion," said Mustafa Shuman, who is among dozens of people who have been camped outside Mursi's palace in Cairo in protest.
Opponents also point out that No votes prevailed in the Cairo area in the first round. They say that shows growing opposition to Mursi, when he cannot win over Egypt's capital.
Islamists, who have won successive ballots since Mubarak's overthrow although by narrowing margins, dismiss charges that they are exploiting religion and say the document reflects the will of a majority in the country where most people are Muslim.
(Additional reporting by Tamim Elyan; Writing by Edmund Blair; Editing by Giles Elgood and Alastair Macdonald)