"The country belongs to you ... protesting lies and fraud is your right," Mousavi, who claims hardline Mahmoud Ahmadinejad won re-election through fraud, said in a statement on his website.
The statement flies in the face of Ayatollah Ali Khamenei, who holds ultimate power in Iran and who last week said the claimed landslide victory of Ahmadinejad was valid.
Echoing Mousavi, former president Mohammad Khatami said in a statement that "protest in a civil manner and avoiding disturbances in the definite right of the people and all must respect that."
But aside from the bold words, the opposition today appeared to be scrambling for a strategy to continue the momentum of the protests that have riveted world attention without putting its supporters in peril. At least 10 people were killed in clashes Saturday between demonstrators and police and the feared Basij militia. Police said Monday that 457 people were arrested that day alone, without saying how many have been arrested throughout the week of turmoil.
Official figures say 17 people have died in the week of unrest. But searing images posted online — including gruesome video purporting to show the fatal shooting of a teenage girl — hint the true casualty toll may be higher in the clashes with police and the feared Basij militia.
Mousavi's website today called for supporters to turn on their car lights in the late afternoon as a sign of protest — a somewhat muted response compared with the recent enormous gatherings.
Also today, the Guardian Council, which agreed last week to investigate some voting complaints, said irregularities were found in 50 constituencies, but that this has no effect on Ahmadinejad's win.
Council spokesman Abbas Ali Kadkhodaei was quoted on the state TV website as saying that its probe showed more votes were cast in these constituencies than there were registered voters, but this "has no effect on the result of the elections."
The acknowledgment of the irregularities was unlikely to mollify the opposition, who allege massive and systematic fraud. Khatami said "taking complaints to bodies that are required to protect people's rights, but are themselves subject to criticism, is not a solution" - effectively accusing the Council of collusion in vote fraud.
Journalists for foreign media have been put under tight restrictions and assessing the extent of the protests and violence is difficult.
The government has intensified a crackdown on independent media — expelling a BBC correspondent, suspending the Dubai-based network Al-Arabiya and detaining at least two local journalists for US magazines.
English-language state television said an exile group known as the People's Mujahedeen had a hand in the street violence and broadcast what it said were confessions of British-controlled agents in an indication that the government was ready to crack down even harder.
The Foreign Ministry today lashed out at foreign media and Western governments, with ministry spokesman Hasan Qashqavi accusing them of "a racial mentality that Iranians belong to the Third World."
"Meddling by Western powers and international media is unacceptable," he said at a news conference shown on state TV, taking particular aim at French President Nicolas Sarkozy.
"How can a Western president, like the French president, ask for nullification of Iranian election results?" Qashqavi said. "I regret such comments."
Mousavi, in statements posted Sunday, warned supporters of danger ahead, and said he would stand by the protesters "at all times." But, he said, he would "never allow anybody's life to be endangered because of my actions" and called for pursuing fraud claims through an independent board.
The former prime minister, a longtime loyalist of the Islamic government, also called the Basij and military "our brothers" and "protectors of our revolution and regime." He may be trying to constrain his followers' demands before they pose a mortal threat to Iran's system of limited democracy constrained by Shiite clerics, who have ultimate authority.
His chances of success within the system would be far higher if he has backers among those clerics.
In the clearest sign yet of a splintering among the ayatollahs, state media announced the arrests Sunday of relatives of former President Hashemi Rafsanjani including his daughter Faezeh, a 46-year-old reformist politician vilified by hard-liners for her open support of Mousavi.
Rafsanjani's relatives, who state media said were held for their own protection, were released after a few hours.
Rafsanjani heads the cleric-run Assembly of Experts, which can remove the supreme leader, the country's most powerful figure. He also chairs the Expediency Council, a body that arbitrates disputes between parliament and the unelected Guardian Council.
Rafsanjani and his family have been accused of corruption by Ahmadinejad. And the 75-year-old ayatollah was conspicuously absent Friday from an address by the country's supreme leader calling for national unity and siding with the president.
That fueled speculation that Rafsanjani, who has made no public comment since the election, may be working behind the scenes and favoring Mousavi.
Ahmadinejad appeared to be courting his own clerical support. State television showed him meeting with mullahs at the presidential palace and telling them the election had demonstrated popular love for the regime.
