Iranian authorities arrested at least 457 people after post-election clashes that left 10 people dead, state radio reported on Monday, as the nation's clerical leaders battled to contain the worst crisis since the Islamic revolution.
Opposition leader Mir Hossein Mousavi, who has led a wave of massive protests over what he says was a rigged presidential election, remained defiant as he urged supporters to continue demonstrating but to adopt "self-restraint."
Iran's electoral watchdog, the Guardians Council, acknowledged of vote discrepancies, saying its preliminary investigation revealed that the number of ballots cast in 50 districts exceeded the number of eligible voters.
Iranian state radio, quoting the police, said the mass arrests were made when demonstrators and security forces clashed on Saturday around the capital's Azadi square in violence that left 10 people dead.
The streets of Tehran were tense on Monday but have remained largely quiet since Sunday and there were no immediate reports of any planned demonstrations. Witnesses said they did not see many security personnel out on the streets.
Mousavi, a post-revolution prime minister who lost to incumbent Mahmoud Ahmadinejad by a landslide according to official results from the June 12 election, told his supporters to continue their protests.
"The revolution is your legacy. To protest against lies and fraud is your right. Be hopeful that you will get your right and do not allow others who want to provoke your anger... to prevail," he said on his newspaper website Kalemeh.
But he urged his supporters -- who have adopted his green campaign colour -- to refrain from violence and show self-restraint, adding: "The nation belongs to you."
A total of 17 people have been killed and many more wounded, according to state media, while hundreds of protestors as well as prominent reformists, journalist and analysts have been rounded up in the post-election turmoil.
World leaders have voiced mounting alarm over the unrest, which has jolted the pillars of the Islamic regime and raised concerns over the future of the Shiite Muslim powerhouse, the fourth largest oil producer in the world.
Iranian leaders have lashed out at "meddling" by Western nations, and accused the foreign media -- already facing tight restrictions on their work -- and the exiled opposition of fomenting the unrest.
The spokesman for the 12-member Guardians Council, which is considering a partial recount after the opposition branded the election a "shameful fraud" and called for a new vote, acknowledged some discrepancies on polling day.
Abbasali Kadkhodai said that in 50 out of the total 366 electoral districts, there were more votes cast than eligible voters.
The defeated candidates have complained that this occurred in up to 170 districts, and have listed a total of 646 irregularities.
British think-tank Chatham House said the results showed "irregularities" in the turnout and "highly implausible" swings to Ahmadinejad, according to an analysis published on Sunday.
There would have to have been a radical shift in rural voting patterns and a "highly unlikely" change of heart among former reformist voters for Ahmadinejad to win as he did, the study concluded.
Ahmadinejad, who had put Iran on a collision course with the West during his first four-year term with his anti-Israeli tirades and defiant stance on the country's nuclear drive, was declared the victor with 63 per cent of the vote.
But in a sign of the divisions emerging among senior Iranian figures over the vote, parliament speaker Ali Larijani said: "A large portion of the people perceived the election result to be different to the one officially announced. This perception must be respected."
Mousavi on Saturday fired off an unprecedented criticism of supreme leader Ayatollah Ali Khamenei who has ruled out any election fraud and warned that opposition leaders would be responsible for "blood, violence and chaos" if there was no end to protests.
On Sunday, Ahmadinejad bluntly told the United States and Britain to stop interfering while Foreign Minister Manouchehr Mottaki accused London of plotting for the past two years to sabotage the election.
"By making hasty comments, you will not have a place in the circle of the Iranian nation's friends. Therefore, I recommend you to correct your interfering positions," Ahmadinejad said.
Dianne Feinstein, who chairs the US Senate Intelligence Committee, backed President Barack Obama's cautious response to the turmoil, saying: "It is very crucial, as I see it, that we not have our fingerprints on this."
British Foreign Secretary David Miliband rejected the charges that protesters were being "manipulated or motivated" by foreign nations and denounced what he said were Iran's effort to turn the election dispute into a "battle" with the outside world.
French Foreign Minister Bernard Kouchner condemned what he called "this brutal repression" while President Nicolas Sarkozy told Qatar's QNA news agency that the attitude of the Iranian authorities was "inexcusable".
In the latest crackdown on the media, Canadian journalist Maziar Bahari of Newsweek has been detained without charge and not been heard of since, the magazine said.
The BBC's permanent correspondent in Tehran has been ordered to leave and the authorities warned the British media of further action if the "interference" continues.