Voters showed up in large numbers Saturday in most of the 17 Egyptian provinces where the second and final round of a referendum on an Islamist-backed draft constitution was taking place, DPA reported.
Queues stretched outside polling stations in Giza, near Cairo; the port city of Port Said; and Luxor, in southern Egypt, as Islamists and the opposition made last-minute efforts to woo voters.
"I read the constitution. It has several good issues such as articles guaranteeing care for the poor," said a veiled female voter in Giza, who gave her name only as Souad. "I hope things will settle and the country becomes stable after the referendum."
Backers and opponents of the charter, drafted by an Islamist-led assembly, have fought street battles about the draft, raising fears that the country could slide into a civil war.
"They should have distributed copies of the constitution to us so that we would be better aware of what we are voting on," said Dina, a voter waiting at a women-only polling station in Giza.
"I have formed my opinion depending on what I heard on TV," she added.
Thousands of military and police forces were deployed across the electoral districts to ensure order.
More than 25 million Egyptians were eligible to vote in Saturday's round, which was under way in areas considered to be broadly conservative, meaning a yes vote was expected to prevail.
About 57 per cent of those who voted in the first round of the referendum, on December 15, approved the document, according to unofficial results.
The opposition claims that the vote was marred by massive irregularities, an allegation denied by the electoral commission after last week's first round.
"We hoped the Islamist supporters would stop the grave breaches committed during the first round, but we were surprised they are using every illegal process in favour of the distorted draft constitution," the opposition April 6 movement said.
State media reported scuffles between supporters and opponents of the constitution in southern Qena province after some people began directing voters to vote "Yes."
In Qalyoubiya province, the armed forces managed to contain clashes that erupted outside a polling station.
Opposition groups monitoring the vote reported that many dead people were still registered to vote. They also said that, in some areas, Christians were prevented from entering polling stations.
President Mohammed Morsi's Muslim Brotherhood and its Islamist allies say the charter will fast-track the country's transition to democracy from the authoritarian rule of president Hosny Mubarak, who was deposed almost two years ago.
The opposition says the constitution could undermine political rights and sideline minorities.
The main opposition bloc, the National Salvation Front, has renewed its call for followers to turn out in large numbers to vote against the charter.
However, Islamists appear confident of securing a clear vote in favour of the constitution.
"We are on the threshold of a decisive historic stage," said Mohammed Badei, the spiritual leader of the Brotherhood.
Polling stations were due to close at 7 pm (1700 GMT), but voting was extended for four hours to accommodate voters, the election committee said.
The final result is to be determined by the majority of the valid ballots cast in both rounds, according to the electoral commission.
If the constitution is adopted, it will clear the way for legislative elections within 60 days. The Islamist-dominated Shura Council, or upper house, will be given the authority to legislate until a new legislature is elected.
If the charter is voted down, an election will be called within three months to pick a new assembly to draft a new constitution.
Meanwhile, Morsi's vice president, Mahmoud Mekki, announced his resignation.
Mekki said he had wanted to resign since November, but postponed his decision due to the unrest in the country, the conflict between Israel and Hamas and the Egyptian-brokered truce that followed. A judge, he said politics was not the profession for him.
According to the draft constitution, the president is not required to appoint a vice president, despite calls for such a requirement by the opposition after the 2011 revolution that ousted Mubarak.