KABUL, Afghanistan (AFP) - The turnout for Afghanistan's presidential election on Saturday could exceed seven million, the head of the Independent Election Commission said - more than half of eligible voters.

Ahmad Yusuf Nuristani said that an estimated 3.5 million people had voted by midday (0830 GMT), five hours after polls opened, 64 per cent of them men and 36 per cent women.

"This figure may have increased to more than seven million by 5pm," he told a news conference. Polls officially closed at 5pm.

Around 13.5 million people were eligible to vote, putting the estimated turnout above 50 percent - a significant increase on 2009 when only around a third of voters cast ballots.

There had been fears that another low turnout would have undermined the legitimacy of whoever succeeds Karzai, who is stepping down after serving the maximum two terms in office.