Hardliner Mahmoud Ahmadinejad steamrolled over one of Iran's best known statesman to win the presidency on Saturday in a landslide election victory that cements conservative control over nation's politicial leadership.

The outcome capped a stunning upset by the Tehran mayor, who many reformers fear will take Iran back to the restrictions imposed after the 1979 Islamic Revolution.

The Interior Ministry gave Ahmadinejad 61.8 per cent of the vote over his moderate rival, Ayatollah Hashemi Rafsanjani, who had 35.7 per cent. The ministry posted a notice declaring Ahmadinejad the winner.

The figures were based on about 54 per cent of the estimated 23 million votes cast, or nearly 49 per cent of Iran's 47 million eligible voters. In last week's election, the turnout was close to 63 per cent.

The victory gives conservatives control of Iran's two highest elected offices - the presidency and Parliament and gives a freer hand to the non-elected theocracy, which hold the final word on all important policies.

Clerics led by supreme leader Ayatollah Ali Khamenei hold true power in Iran, able to overrule elected officials. But reformers, who lost Parliament in elections last year, had been hoping to retain some hand in government to preserve greater social freedoms they've been able to win, such as looser dress codes, more mixing between the sexes and openings to the West.

Ahmadinejad supporters will go to mosques to hold prayers and 'thank God for this great victory,' said his campaign
manager Ali Akbar Javanfekr. But he said no street celebrations were planned.