Mahmoud Ahmadinejad has been confirmed as president and a row over his June 12 re-election has ended, Iran has said.

The Guardian Council, the country's top legislative body, said a partial recount on Monday had disproved complaints of irregularities by pro-reform opponents.

There has been little sign of major unrest in the capital Tehran of late, in contrast to protests by tens of thousands that erupted when the hardliner was first declared winner of the presidential poll.

Opposition supporters say the vote was rigged to favour Mr Ahmadinejad over reformist rivals including Mir Hossein Mousavi, who came second. Mr Mousavi had rejected the idea of a recount and sent no representatives to watch it.

At least 20 people died in subsequent violence which the government and opposition blamed on one another. Pro-government Basij militia and riot police broke up the protests.

State broadcaster IRIB said: "The secretary of the Guardian Council, in a letter to the interior minister, announced the final decision of the Council ... and declares the approval of the accuracy of the results of ... the presidential election."

The poll and its turbulent aftermath have exposed splits in Iran's political establishment and plunged the country into its deepest crisis since the 1979 Islamic Revolution.

But options for the opposition look limited now the election result has been officially upheld, after the recount of what the council said was a random 10 per cent of the vote.

On June 19, Supreme Leader Ayatollah Ali Khamenei signalled that mass protests would no longer be tolerated.

US Secretary of State Hillary Clinton has said Iran's rulers are still likely to face internal opposition.

"They have a huge credibility gap with their own people as to the election process. And I don't think that's going to disappear by any finding of a limited review of a relatively small number of ballots," she said.

Asked if Washington would recognise Ahmadinejad as president of the world's fifth biggest oil exporter, she said: "We're going to take this a day at a time."

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