Voters entered polling stations shortly after 8 a.m. to decide between Mubarak and his nine challengers, who are mostly obscure leaders of small political parties. Only liberal candidates Ayman Nour and Noman Gomaa have significant political standing.
Rival candidates immediately began complaining that the government interfered with the election to help Mubarak, and hundreds of protestors assembled in Cairo to call for voters to boycott. The government, however, had banned demonstrations on Election Day, and plainclothes men attacked some protestors and dispersed the crowd.
Mubarak agreed to hold elections this year after the United States and some Egyptian politicians urged him to reform the single candidate referendum system that had brought him to office four times since 1981.
But opposition groups charge that the 77-year-old Mubarak has no interest in actual political change, and the government refused to allow the nation's biggest opposition group, Islamist Muslim Brotherhood, to create a political party.
"This is not an election," said Nour, 40, who is running for the Ghad (Tomorrow) Party. "They are treating this as another referendum. The government has lied (about a fair vote)."
At a news conference, Nour said the ruling National Democratic Party and municipality workers were paying voters the equivalent of $3 or $9 to support Mubarak. He also said election officials refused to let some of his supporters legally enter polling stations and that the ink used to mark those who had already voted was not indelible, making it possible for them to cast another vote.
"They (the authorities) are exposing Egypt to destructive danger for the sake of these petty acts. It would have been wiser for Hosni Mubarak to win by a small margin or even lose, than that he should win in a fabricated or forged way," Nour said.
Polling stations in Egypt, the Arab world's most populous nation with 72 million people, close at 10 p.m. and the outcome is expected by the weekend.