Long queues had already formed outside some voting stations before the polls opened at 6am GMT with police and army deployed outside, according to AFP reporters.

Muslim Brotherhood candidate Mohammed Mursi has promised that an Egypt under his leadership would be inclusive and vowed to defend the goals of last year's uprising, while ex-prime minister Ahmed Shafiq is running on a tough law-and-order platform.

"I will vote for the one who will guarantee security and safety for our community," said Makram, a Coptic Christian voter, from a polling station in the Shoubra neighbourhood.

Over in Manial, an island in the Nile, a crowd including veiled and unveiled women waited to cast their ballots.

"I'm voting for Mursi because I don't want Shafiq to win. I'm scared of Mursi but I'm more scared of Shafiq," said Nagwan Gamal, 26, a teaching assistant.

The race has polarised the nation, dividing those who fear a return to the old regime under Shafiq's leadership from others who want to keep religion out of politics and fear the Brotherhood would stifle personal freedoms.