| The Muslim Brotherhood has provided the highest-profile support for the referendum [Reuters]
Millions of Egyptians have turned out for today's constitutional referendum, the first vote following the overthrow last month of Hosni Mubarak, the country's long-serving president.
Voters are deciding on a package of nine amendments, about half of which deal with the conduct of elections. One would make it easier for independent candidates to run for president; another would re-establish judicial oversight of elections.
The amendments were drafted by an eight-man constitutional committee, which was appointed by the ruling military junta. They must be approved or rejected as a bloc.
There were early reports of high turnout, with voters in some districts predicting an hours-long wait before they would be able to cast their ballots.
"This is an historic day for Egypt," said Yahya al-Gamal, the country's deputy prime minister, after casting his vote in Cairo. "I have never seen such large numbers of voters in Egypt. Finally, the people of Egypt have come to realise that their vote counts."
Voters also reported some irregularities: Some polling centres in Giza, Mohandiseen, 6th of October City and other districts were reportedly handing out ballots without the required official stamp. Ballots without a stamp on the back can be discarded as illegitimate.
An uncertain outcome
Most of the amendments have been longtime demands of the Egyptian opposition - but most of the country's opposition parties are urging voters to reject them. Critics want a completely new constitution; they say these modest changes do not do enough to limit the powers of the president.
Amr Moussa, the outgoing Arab League chief and a front-runner for Egypt's forthcoming presidential election, has urged a "no" vote; so has former IAEA director Mohamed ElBaradei.
The youth activists that drove Egypt's revolution have also decided to oppose the amendments: The Revolution Youth Council held an internal vote earlier this week and, while it decided to participate in the referendum, it urged people to vote "no."
"Most of the people who triggered the revolution are going to say no," ElBaradei said.
The highest-profile support has come from the Muslim Brotherhood, which has plastered many Cairo neighbourhoods with posters urging voters to approve the amendments.
Supporters say a "yes" vote will hasten a return to civilian rule: If the amendments are approved, Egypt is scheduled to hold parliamentary elections in June, and a presidential election in September. If the amendments are defeated, the parliamentary election could be postponed until December while a committee works on revising the constitution.
Polls suggest the outcome of the vote will be close. One survey earlier this week found that 60 per cent of eligible voters planned to vote "no."
About 45 million people are eligible to vote. They will do so using their national ID cards, a key change from Mubarak-era elections, when voters were required to pre-register for elections - a process often subject to fraud and intimidation.
Polls will close at 7pm local time [17:00 GMT], though some polling centres in southern Egypt will remain open until 9pm.