President Mahmoud Ahmadinejad on Sunday said any country that dared to attack Iran would "deeply regret" such a move, dashing hopes that his re-election Saturday would temper his confrontational stance toward the world.
"Who dares to attack Iran? Who even dares to think about it?" Ahmadinejad said at a news conference in response to a question.
Iran's refusal to halt nuclear work the West suspects is aimed at making bombs, a charge Tehran denies, has sparked persistent speculation that Israel or the United States might strike at the country's nuclear facilities.
Ahmadinejad added that Iran's nuclear issue "belongs in the past," indicating there would be no change in nuclear policy during his second term in office.
Meanwhile, defeated presidential candidate Mir Hossein Mousavi formally appealed against Iran's election result on Sunday to the legislative body, the Guardian Council, a statement on his website said.
"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."
Iranian police again clashed on Sunday with demonstrators protesting in Tehran against his re-election.
Supporters of defeated reformist Mir Hossein Mousavi, who has dismissed Ahmadinejad's victory in Friday's election as a "dangerous charade", gathered in the city centre, 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.
In Sunday's news conference, Iranian President Mahmoud Ahmadinejad also defended his re-election as "clean and healthy," dismissing complaints by defeated candidates as sour grapes.
"They may be upset by their failure," he said. "They spent lot of money to make propaganda [and] expected to win so it is natural they are disappointed and upset."
"The margin between my votes and the others is too much and no one can question it."
Reports: Iran rounds up Mousavi, 100 reformists
Sunday's clashes came after reports that more than 100 Iranian reformists, including Mousavi, were arrested on Saturday night.
Mohammad Ali Abtahi, a leading reformist, said that the brother of former president Mohammad Khatami was among the detainees. The L.A. Times reported Sunday that Mousavi, the main challenger to Ahmadinejad, had been put under house arrest.
"They were taken from their homes last night," Abtahi said. He said more arrests were expected.
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.
Authorities released Khatami's brother on Sunday, his wife, Zahra Eshraghi, told The Associated Press.
She said at least two other top leaders of Iran's largest reformist party, the Islamic Iran Participation Front, including the party's secretary-general, were also released early Sunday after they were arrested when police stormed the party's headquarters on Saturday. Several others remained in custody, she said.
The arrests seemed aimed at avoiding a repeat of the chaos that lasted past midnight Saturday. Opponents of President Mahmoud Ahmadinejad set buses and cars ablaze in the capital and threw rocks at police to protest what they viewed as his illegitimate victory.
Iran filters Internet in apparent bit to undercut liberal voices
Iran restored cell phone service that had been down in the capital since Saturday. But Iranians could not send text messages from their phones, and the government increased its Internet filtering in an apparent bit to undercut liberal voices.
Web sites linked to Mousavi, who declared himself the true winner of Friday's presidential race and urged backers to resist the government, were down. Social networking sites including Facebook and Twitter were also not working.
The restrictions were likely intended to prevent Mousavi's supporters from organizing large-scale protests. But several small groups took to the streets, according to witnesses. About 300 Mousavi supporters gathered outside Sharif University, chanting "Where are our votes?"
About a dozen riot police descended upon a crowd of some 50 Mousavi supporters standing outside his campaign quarters, beating them with batons and causing them to disperse.
Reports that Mousavi was under house arrest could not be confirmed, but the 67-year-old former prime minister has not been seen in public since he gave a late night press conference Friday where he accused the government of voter fraud. On Saturday, Mousavi released a Web message saying he would not surrender to this manipulation.
Tehran deputy prosecutor, Mahmoud Slarkia, told the semi-official ISNA news agency that less than 10 people were arrested on the charge of disturbing public opinion through their false reports on Web sites after the election. He did not mention any names.
Iran's deputy police chief Ahmad Reza Radan said some of Saturday's protesters were detained and police used tear gas to stop the demonstrations. He said the situation was under control and accused the foreign media of exaggerating the protests to show unrest in Tehran.
Police will not allow protesters to disturb the peace and calmness of the people under the influence of foreign media, Radan said on state television, which showed footage of the protests for the first time Sunday.
Ahmadinejad: Foreign media coverage harming Iranian people
Ahmadinejad also accused the foreign media of producing coverage that harmed the Iranian people in an address to the country broadcast on state TV late Saturday, saying "a large number of foreign media ... organized a full-fledged fight against our people."
He did not mention the unrest, saying only a new era has begun in the history of the Iranian nation. Ahmadinejad is scheduled to hold a massive rally with supporters Sunday afternoon in central Tehran.
Slarkia, the deputy prosecutor, confirmed that Iran was blocking five pro-Mousavi Web sites because of election violations.
The U.S. has refused to accept Ahmadinejad's claim of a landslide re-election victory said it was looking into allegations of election fraud. There are no independent election monitors in Iran.
U.S. Secretary of State Hillary Rodham Clinton said Saturday she hoped the outcome reflects "the genuine will and desire of Iranian voters."
The European Union also said it was concerned about alleged irregularities during Friday's vote.
Past Iranian elections were considered generally fair. In 2005, when Ahmadinejad was first elected, the losing candidates claimed irregularities at the polls, but the charges were never investigated.
Mousavi called on his backers to avoid violence, but he is still talking tough about pressing his claims of election fraud. He charges the polls closed early but has not fully outlined all of his fraud allegations.
There also have been no hints of any new policy shifts on key international issues such as Iran's standoff over its nuclear program and the offer by President Barack Obama to open dialogue after a nearly 30-year diplomatic estrangement. All high-level decisions are controlled by the ruling theocracy.