Islamists backing a new constitution for Egypt claimed victory Sunday in an initial phase of a referendum, but the opposition alleged polling violations and said it will await the results from the final round in a week's time.
The two sides' positions drew out the deep uncertainty and division seen in Egypt over the past three weeks, a period marked by mass protests and deadly clashes.
A majority of 56.5 percent voted for the draft charter put to half of Egypt's 51 million voters on Saturday, according to the Freedom and Justice Party, the political branch of President Mohamed Morsi's Muslim Brotherhood.
Egyptian media reported roughly the same figure, which fell short of the landslide the Brotherhood had been hoping for to quiet the restive opposition.
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 reiterated its allegation that balloting had been "marred by irregularities and violations".
The head of the Front, Mohamed ElBaradei, a former chief of the UN nuclear energy agency, tweeted of the first round: "Country split, flagrant irregularities, low turnout, disillusion w(ith) Islamists on the rise. Illiteracy remains a hurdle."
Several Egyptian rights and monitoring groups also said in a joint statement that 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, and 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.
Violence between the charter's supporters and opponents flared in Egypt's two largest cities, Cairo and Alexandria, just before and after the referendum, with police repelling an Islamist attack on the liberal Wafd party headquarters in the capital on Saturday night.
On December 5, clashes between pro- and anti-Morsi protesters outside the presidential palace killed eight people injured hundreds, prompting the army to deploy troops and tanks around the compound.
If the constitution is approved, Morsi hopes it will end a tumultuous transition almost two years after a popular uprising overthrew president Hosni Mubarak and ushered in interim military rule before Morsi's election in June.
Liberals and Christians had boycotted the assembly that drafted the charter, complaining the Islamist-dominated panel had ignored their concerns.
The Brotherhood and its Freedom and Justice Party threw its formidable organisational machine behind a "yes" campaign for the draft constitution.
But many opposition voters were especially hostile towards the Brotherhood, which the National Salvation Front believes wants to usher in strict Islamic laws.
International watchdogs, the UN human rights chief, the United States and the European Union have all expressed reservations about the draft because of loopholes that could be used to weaken human rights.
Analysts said it was likely -- but not certain -- that the draft constitution would be adopted.
Hisham Kassem, an analyst based in Cairo, told AFP the Muslim Brotherhood used "intimidation" to bolster the "yes" vote.
"And in the countryside it's easier to rig, so it's probably going to go their way."
Kassem predicted that if the new charter is adopted, that "is likely to take the country into some sort of paralysis or civil disobedience".
A "serious crisis" would also likely ensue for Egypt's already debilitated economy, he added.