Iranian police again clashed on Sunday with people protesting in Tehran against the re-election of hardline President Mahmoud Ahmadinejad, who said the vote had been clean.

The unrest that has rocked Tehran and several other cities since official results were declared on Saturday is the sharpest expression of discontent against Iran's leadership for years.

Tens of thousands of flag-waving Ahmadinejad partisans converged on the capital's Vali-e Asr square ahead of a victory speech by the man who won Friday's vote by a surprising margin.

Supporters of defeated moderate Mirhossein Mousavi, who has dismissed Ahmadinejad's triumph as a dangerous charade, earlier gathered in central Tehran, chanted his name and threw stones at police, a Reuters witness said.

Police on motorcycles drove through the crowd to disperse the protesters. At least one person, a woman, was injured. Police briefly detained journalists filming the violence.

Ahmadinejad consigned Iran's nuclear dispute to the past, signaling no nuclear policy change in his second term, and warned that any country that attacked his own would regret it.

Who dares to attack Iran? Who even dares to think about it? he said at a news conference.

Iran's refusal to halt nuclear work the West suspects is aimed at making bombs, a charge Tehran denies, has sparked talk of possible U.S. or Israeli strikes on its nuclear sites.

NOT GOOD NEWS

France signaled its concern over events in Iran in the strongest public comments yet from a major Western power.

What is happening in Iran is clearly not good news for anyone, neither for the Iranians nor for peace and stability in the world, Henri Guaino, one of French President Nicolas Sarkozy's closest advisers, told France's Europe 1 radio.

French Foreign Minister Bernard Kouchner said repression of opponents was closing off dialogue. Brutality and never-ending military development will not bring any solutions, he said.

Ahmadinejad described the election as clean and healthy, dismissing complaints by defeated candidates as sour grapes.

They may be upset by their failure, he said. They spent a lot of money to make propaganda (and) expected to win, so it is natural they are disappointed and upset.

Police have detained more than 100 reformers, including the brother of former President Mohammad Khatami, a leading reformer said on Sunday. A police official confirmed some detentions.

Ahmadinejad was planning celebrations in the capital later on Sunday. His unexpectedly overwhelming victory and its violent aftermath raised fresh questions about how Iran will respond to U.S. President Barack Obama's diplomatic overtures.

Analysts said the election result would disappoint Western powers trying to convince the world's fifth biggest oil exporter to halt sensitive nuclear work. Obama has urged Iran's leadership to unclench its fist for a new start in relations.

Mohammad Ali Abtahi, who served as a vice president under Khatami, told Reuters the former president's brother, Mohammad Reza Khatami, was among more than 100 members of Iran's biggest reformist party, Mosharekat, who were held on Saturday.

There are reports a political party was involved in yesterday's incidents. Some of them have been arrested, Iran's deputy police chief Ahmed Reza Radan was quoted by the Fars news agency as saying. He denied Khatami was among them.

TIRED OF DICTATORSHIP

Mousavi's wife, Zahra Rahnavard, denied reports that her husband had been detained or put under house arrest.

The Iranian people voted to change Ahmadinejad, but this vote became a vote to solidify Ahmadinejad. People are tired of dictatorship, said Rahnavard, who took a high-profile public role in her husband's election campaign, which drew tens of thousands of supporters onto the streets of Tehran.

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, she told Reuters.

An aide to Rahnavard said she had tried to speak at Tehran University on Sunday, but had been prevented.

Mousavi has rejected Ahmadinejad's victory, saying it had been achieved by vote-rigging that would jeopardize the pillars of the Islamic Republic and will establish tyranny.

Interior Ministry officials have rejected accusations of fraud and Supreme Leader Ayatollah Ali Khamenei, Iran's top authority, has called on Iranians to back their president.

A senior Western diplomat in Tehran said he believed the authorities would soon subdue the street unrest, but said Ahmadinejad's re-election battle had exposed a polarizing power struggle between radicals and moderate conservatives which could affect the Islamic Republic's long-term stability.

There is turbulence in the whole system, he added.

Protests also broke out on Saturday in the cities of Tabriz, Orumieh, Hamedan and Rasht, where crowds chanted for Mousavi.

In Isfahan, police made arrests after students at Sanati University set equipment and furniture on fire, a witness said.

In Tehran, municipality spokesman Mohammad Hadi Ayazi said protesters had torched seven buses on Saturday, destroyed 60 rubbish bins and set several banks on fire.

(Additional reporting by Fredrik Dahl; editing by Alistair Lyon)

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