The Islamist group the Muslim Brotherhood has said Egypt's controversial new constitution passed with 64 percent of the vote, while opposition leaders have called for investigations of alleged voter fraud.
Egypt's opposition called Sunday for an investigation into allegations of vote fraud in the referendum on a deeply divisive Islamist-backed constitution after the Muslim Brotherhood, the main group backing the charter, claimed it passed with a 64 percent "yes" vote.
Official results have not been released yet and are expected on Monday. If the unofficial numbers are confirmed, it will be a victory Islamist President Mohammed Morsi, who is from the Brotherhood.
But for many Egyptians, especially the tens of millions who live in extreme poverty, the results are unlikely to bring a hoped for end to the turmoil that has roiled their country for nearly two years since the uprising that ousted authoritarian leader Hosni Mubarak.
The opposition allegations look likely to prolong the struggle that has exploded in deadly street violence at times over the past month, ensuring that stability will remain elusive.
"The referendum is not the end game. It is only a battle in this long struggle for the future of Egypt," said the National Salvation Front, the main opposition group. "We will not allow a change to the identity of Egypt or the return of the age of tyranny."
The opposition claims the new constitution seeks to enshrine Islamic rule in Egypt and accuses the Islamists of trying to monopolize power.
Critics say it does not sufficiently protect the rights of women and minority groups and empowers Muslim clerics by giving them a say over legislation. Some articles were also seen as tailored to get rid of Islamists' enemies and undermine the freedom of labor unions.
The opposition front said it filed complaints to the country's top prosecutor and the election commission asking for an investigation.
"The results of the referendum are for sure because of the rigging, violations and mismanagement that characterized it," the opposition group said.