Defeated Iranian reformist Mir-Hossein Mousavi calls for more protest against Mahmoud Ahmadinejad

Mir-Hossein Mousavi said he would not give up the struggle despite President Mahmoud Ahmadinejad being declared the winner with 62.4 per cent of the vote.

Mr Mousavi disclosed that he had appealed to the Council of Guardians, a powerful committee of 12 clerics, to formally cancel the result.

"I have submitted my official formal request to the Council to cancel the election result," he said in a statement. "I urge you, the Iranian nation to continue your nationwide protests in a peaceful and legal way."

Mr Ahmadinejad insisted the contest had been "clean" and said the popular demonstrations which swept Tehran were "like the passions after a football match".

But in a second day of clashes, scores of young people shouted "Death to the dictator!" and broke the windows of city buses on several streets in central Tehran. They burned banks, rubbish bins and piles of tyres used as flaming barricades. Riot police hit some of the protesters with batons while dozens of others holding shields and motorcycles stood guard nearby.

The authorities moved to prevent any more demonstrations by arresting 170 people in a series of raids across Tehran.

They included reformist politicians, notably Mohammed Reza Khatami, the brother of a former president of Iran, and other people suspected of organising Saturday's demonstrations. Mr Khatami, who was an MP until he was banned from standing in the 2004 parliamentary election, was taken from his home but later released.

Meanwhile, the director of the BBC's World Service accused the Iranian Government of jamming its broadcasts to the country.

Peter Horrocks said audiences in Iran, the Middle East and Europe had been affected by an electronic block on satellites used to broadcast the BBC Persian TV signal to Iran.

He said: "It seems to be part of a pattern of behaviour by the Iranian authorities to limit the reporting of the aftermath of the disputed election."

Mr Mousavi, a former prime minister who ran for the presidency with the support of powerful figures in Iran's regime, called for his supporters to avoid violence but angry protesters continued to take to the streets, setting light to vehicles and throwing stones in Tehran.

His wife, Zahra Rahnavard, denied reports her husband had been put under house arrest but added: "People are tired of dictatorship.

"People are tired of not having freedom of expression, of high inflation, and adventurism in foreign relations. That is why they wanted to change Ahmadinejad."

Anger grew over the weekend after a high turnout, estimated to be 85 per cent, raised hopes among Mr Mousavi's supporters that the election result would be close.

But officials then announced Mr Ahmadinejad had won a landslide victory with almost two thirds of the vote.

It prompted Mr Mousavi to call for the result to be cancelled but Iran's Council of Guardians is packed with hardline supporters of Mr Ahmadinejad and it seems highly unlikely they will agree to the request.

Ayatollah Ali Khamenei, the Supreme Leader, has also endorsed the election and urged all Iranians to rally behind Mr Ahmadinejad.

The president held a rally for supporters in Tehran and proclaimed that Iranian elections were the "cleanest" in the world. Mr Ahmadinejad added: "Today, we should appreciate the great triumph of the people of Iran against the unified front of all the world arrogance."

His re-election amounted to a victory over the "psychological war launched by the enemy", he said.

During an earlier press conference, Mr Ahmadinejad dismissed the protests.

"Some believed they would win, and then they got angry," he said. "It is like the passions after a football match." He added: "The margin between my votes and the others is too much and no one can question it."

International reaction to the election result suggested that Mr Ahmadinejad would not be viewed as a legitimate leader.

Joe Biden, the US vice-president, said he had an "awful lot of doubt" about the credibility of the vote.

He said: "It sure looks like the way they're suppressing speech, the way they're suppressing crowds, the way in which people are being treated, that there's some real doubt about that.

"I don't think we're in a position to say. What surprised me in that the assertion that he won by 60 something per cent of the vote, and so I think we have to wait and see. But it didn't seem on its face to be as clear cut."

Meanwhile, the European Union said it was "concerned about alleged irregularities". Bernard Kouchner, the French foreign minister, criticised the "brutal reaction" of the regime's security forces to the demonstrations.