Muslim Brotherhood candidate Mohammed Morsi was surrounded by supporters as he arrived at a polling station on the first of two days of presidential elections in Egypt.
Morsi, who finished in first place in the previous round with 24.8 percent, held a press conference on Saturday alleging electoral violations.
His opponent in the run-off is Ahmed Shafiq, who served as the last prime minister under former leader Hosni Mubarak.
Shafiq polled close to 23.7 percent in the first round, but is seen by some as a candidate who represents the old regime. He denies being supported by the ruling military council.
However, there appears to be less enthusiasm for this round, with some protesting against both candidates.
Queues of voters stretched outside polling stations, causing polling to be extended by one hour on Saturday to 21:00 local time. There will be at least 12 hours of voting on Sunday.