Opposition groups in Egypt have called for nationwide protests ahead of the second leg of the constitutional referendum to be held next weekend, after alleging polling violations in the first round.
Supporters of the draft document claimed victory in the first leg on Sunday after the Muslim Brotherhood's Freedom and Justice Party (FJP) said that a majority of 56.5 per cent voted in favour of it.
But the opposition National Salvation Front coalition said it would "not recognise any unofficial result," and would wait for the formal tally after next Saturday's second round of voting.
It called on Egyptians to "take to the streets on Tuesday to defend their freedoms, prevent fraud and reject the draft constitution."
It reiterated its allegation that balloting had been "marred by irregularities and violations".
The FJP had representatives posted at almost every polling place in the 10 areas where the referendum took place on Saturday.
Egyptian media reported roughly the same figures, which fell short of the landslide the Brotherhood had been hoping for to quiet the restive opposition.
"Country split, flagrant irregularities, low turnout, disillusion w(ith) Islamists on the rise. Illiteracy remains a hurdle," Mohamed ElBaradei, head of the Front and former chief of the UN nuclear energy agency, said on Twitter.
Several Egyptian human rights and monitoring groups claimed there were irregularities and demanded Saturday's vote be done over.
They alleged monitors were excluded from some polling stations, judges were not present in all as required and some fake judges were seen. Some also alleged that women were prevented in some cases from casting their ballot.
The electoral commission, "in the interest of national consensus", must "recognise that it was not capable (of ensuring) good organisation and it must redo the referendum," said Negad el-Borei, a spokesman for one of the groups, which represents lawyers.
Potentially adding to questions over the legitimacy of the vote is the low turnout in the first round - unofficially estimated at 32 per cent, which if confirmed would be far lower than the presidential or parliamentary elections following Hosni Mubarak's fall.
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Mohamed Morsi, the Egyptian president, and his supporters say the constitution is vital in order to move forward with the country's democratic transition. Opponents say that the basic law is too heavily influenced by religion, and that it tramples on minority rights.
The build-up to the vote was marked by deadly protests, with demonstrations held across the country by both opponents and supporters of the document.
The protests first started when Morsi accorded himself sweeping new powers and fast-tracked the constitution through an assembly dominated by allies from the FJP.
At least eight people were killed and several hundred injured in a series of clashes between the two camps.
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 were eligible to vote in the first round.
To ensure security during the referendum, 120,000 troops were deployed to reinforce 130,000 police.