Reuters reports: An Islamist-backed Egyptian constitution won approval in a referendum, rival camps said on Sunday, after a vote the opposition said would sow deep social divisions in the Arab world’s most populous nation.

The Islamist Muslim Brotherhood, which propelled President Mohamed Mursi to power in a June election, said an unofficial tally showed 64 percent of voters backed the charter after two rounds of voting that ended with a final ballot on Saturday.

An opposition official also told Reuters their unofficial count showed the result was a “yes” vote, while party spokesmen said there had been a series of abuses during the voting.

The main opposition coalition, the National Salvation Front, responded to the defeat by saying it was moving towards forming a single political party to challenge the Islamists who have dominated the ballot box since strongman Hosni Mubarak was overthrown two years ago.

Members of the opposition, taking heart from a low turnout of about 30 percent of voters, pledged to keep up pressure on Mursi through peaceful protests and other democratic means.