CAIRO - Egyptian rights groups called Sunday for a repeat of the first round of the constitutional referendum, alleging the vote was marred by widespread violations. Islamists who back the disputed charter claimed they were in the lead with a majority of "yes" votes, though official results have not been announced.

Representatives of seven rights groups charged that there was insufficient supervision by judges in Saturday's vote in 10 of Egypt's 27 provinces and that independent monitors were prevented from witnessing vote counts.

The representatives told a news conference that they had reports of individuals falsely identifying themselves as judges, of women prevented from voting, and of members of Islamist President Mohammed Morsi's Muslim Brotherhood being allowed inside polling stations. They also complained that some polling centers closed earlier than scheduled and that Christians were denied entry to polling stations.

Mohamed ElBaradei, Egypt's best known reform leader, was as frustrated by how the referendum was run as the rights groups.

"Is a referendum held under insufficient judicial supervision, clearly tenuous security and the violence and violations we are witnessing the road to stability or playing with the country's destiny?" the Nobel Peace laureate and former U.N. nuclear agency chief tweeted.

The vote is the latest stage in a nearly two-year struggle over Egypt's identity since the ouster of longtime leader Hosni Mubarak in a popular uprising. The latest crisis over the Islamist-backed charter evolved into a fight - deadly at times - over whether Egypt should move toward a religious state under Morsi's Brotherhood and its ultraconservative Salafi allies, or one that retains secular traditions and an Islamic character.

Underlining the tension, about 120,000 army troops were deployed to help the police protect polling stations and state institutions after clashes between Morsi's supporters and opponents over the last three weeks left at least 10 people dead and about 1,000 wounded.

Potentially adding to questions over the legitimacy of the vote is the low turnout in the first round - unofficially estimated at 32 percent, which if confirmed would be far lower than the presidential or parliamentary elections after Mubarak's fall. A second round is to be held in the remaining 17 provinces Saturday.

Those who did vote were deeply divided. The Brotherhood claimed about 57 percent voted in favor of the draft.