Defeated presidential candidate Mir Hossein Mousavi formally appealed the result of Iran's election on Sunday and called on his supporters to keep up their "peaceful" protests as they continued to clash with police in Tehran following the arrest of more than 100 reformists.
Ahmadinejad dismissed Tehran’s worst unrest in a decade as "not important" and said Friday's vote was "real and free."
Tens of thousands marched in support of Ahmadinejad waving Iranian flags and shouting his name along Tehran's Vali Asr street, where just a week before supporters of rival candidate Mir Hossein Mousavi held a huge pre-election rally.
Earlier in the day police fired on supporters of defeated moderate reformist Mousavi who had gathered in the city center, chanting his name and throwing stones at police
The police chief said all gatherings without permits would not be permitted and said the candidates would be held responsible for an violations.
Meanwhile, Mousavi launched an official appeal contesting the election results late Sunday afternoon.
"Today, I have submitted my official formal request to the council to cancel the election result," Mousavi said in the statement. "I urge you Iranian nation to continue your nationwide protests in a peaceful and legal way."
The unrest that has rocked Tehran and several other cities since official results were declared on Saturday is the sharpest expression of discontent with Iran's leadership for years and appears to have galvanized a grass-roots movement for change in the Islamic republic, where 60 percent of the population was born after the revolution.
Meanwhile sources close to Mousavi said he was in a "safe place" without offering further detail.
Earlier in the evening Mousavi called on authorities to cancel the election as the only way to restore public trust. Mousavi, who has accused authorities of election fraud, urged his supporters to continue their "civil and lawful" opposition to the results and advised police to stop violence against protesters.
Mousavi's wife, Zahra Rahnavard, had denied earlier reports that her husband himself had been detained or put under house arrest.
"He is following the issue of the election. He says he is with the people and beside them," Rahnavard said.
"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 said.
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, in the vote which officials said attracted a record turnout of around 85 percent of the 46 million electorate 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.
The election highlighted deep divisions in Iran after four years under Ahmadinejad, who had massive support in the rural heartland and among the poor, while in the big cities young men and women threw their weight behind Mousavi.
Officials blocked communication in the capital, closing down Iran's main cellular phone network, SMS mobile phone messaging services and blocking several reformist websites and social networking site Facebook.
Al Arabiya's Tehran bureau was closed for a week beginning Sunday without explanation by the ministry charged with foreign press accreditation.
Police briefly detained journalists filming the violence during the pro-Mousavi protests.
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.
Police detained more than 100 reformists Sunday, including the brother of former President Mohammad Khatami and Mousavi’s four closest advisors. The granddaughter of revolutionary founder Ali Khamenei was under house arrest. A police official confirmed some detentions.
Mohammad Ali Abtahi, who served as a vice president under Khatami, told Reuters the former president's brother Mohammad Reza Khatami was one of more than 100 members of Iran's biggest reformist party Mosharekat who were held on Saturday.
A judiciary spokesman said they had not been arrested but that they were summoned and "warned not to increase tension." They were later released, he said.
"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 said Khatami was not among 10 people arrested, but did not say if he had been summoned and released.
Analysts said the election result would disappoint Western powers trying to convince the world's fifth biggest oil exporter to halt nuclear activities they suspect are aimed at making bombs. Obama had urged Iran's leadership "to unclench its fist."
U.S. Secretary of State Hillary Clinton said the United States was monitoring the outcome of the election closely and hoped the result reflected the will of the Iranian people.
White House Press Secretary Robert Gibbs said in statement that the U.S. was "impressed by the vigorous debate and enthusiasm that this election generated, particularly among young Iranians."
"We continue to monitor the entire situation closely, including reports of irregularities," he said.
French Foreign Minister Bernard Kouchner voiced concern about events in Iran after the election, saying "brutal" repression of opponents was closing the door to dialogue.
"Brutality and never-ending military development will not bring any solutions," Kouchner said after meeting U.S. special envoy to the Middle East George Mitchell in Paris.
Khatami calls for new vote
The clerical group of former reformist president Mohammad Khatami called on for a re-staging of the presidential vote.
The Combatant Clerics' Assembly, whose members comprise reformist and moderate clerics, expressed concern at a "massive engineering of votes" in Friday's election -- echoing comments Mousavi.
"The assembly concludes that annulling this election and repeating the vote in a fairer and more logical atmosphere is the right way to retrieve public trust and sustain the national reconciliation with voting," it said in a statement.