Vote counting has begun in Cairo and Alexandria after polling stations closed for a controversial constitution referendum that has deepened divisions in the nation.

Polling stations in half the country were tallying the results early on Sunday, after voting had been extended by four hours due to high turnout.

The second round of the referendum is to be held next Saturday, after which the official result is to be given.

In order to pass, the constitution must be approved by more than 50 per cent 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.

"I do not like to predict anything until after the vote counting is complete. We have now finished with one ballot

box and the second ballot box is almost ready for counting," said supervising judge Maha Fathy at a polling station in Cairo.

"The process is easy because it's just between a yes or a no vote and after the counting you can get the full results

even before we send it off to the official committee," she added.

Egypt has been in turmoil, nearly two years after the fall of Hosni Mubarak, and Morsi's efforts to return the Arab world's biggest nation to normality have been hampered by what the opposition views as his autocratic tendencies.

The measure is generally expected to pass, given the well-organised Muslim Brotherhood's record of winning elections since the fall of Mubarak. But 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.  Source: Aljazeera