Tens of thousands of protesters are gathering in Tehran amid reports that opposition leader Mir Hossein Mousavi is speaking at a mass rally Monday.
The crowd - many wearing the trademark green color of Mousavi's campaign - streamed through the streets and headed toward the capital's huge Freedom Square in the largest display of opposition unity since Friday's elections ended with Mousavi claiming widespread fraud in President Mamoud Ahmadinejad's declared victory.
"The vote of the people is more important than Mousavi or any other person," French news agency AFP reported Mousavi told the crowd.
According to a Twitter account bearing Mousavi's name, the opposition leader reportedly spoke from the roof of a car and declared he was ready to stand in another election.
A subsequent Twitter post links to a photo of Mousavi presumably speaking at the rally.
Riot police who had been attacking demonstrators Sunday are present, but for the moment, they are just lining the route. The crowds are being allowed to walk past the University Of Tehran and are being funneled down a street near it, CBS News correspondent Elizabeth Palmer reports from Tehran.
"It's very peaceful," reports Palmer. "Somehow a nucleus of people gathered at the university and the word spread and thousands and thousands of mostly young people have been streaming down through the city together.
Iranian authorities banned anti-government protesters from staging the planned rally as the country's supreme leader, Ayatollah Ali Khamenei, reportedly into claims of election fraud.
But protesters have turned out in spite of the ban.
Riot police and some soldiers were present at the scene, but the atmosphere was relaxed, report Palmer.
Palmer reports that Mousavi hadn't been seen in public since election day. He has been under house arrest and Palmer reports that several other prominent opposition figures have been taken into custody.
The Iranian regime has cracked down on the flow information inside the country, blocking most social networking sites, many phone lines and Internet services. Foreign journalists are being urged to leave the country, reports Palmer.
Mousavi, who served as prime minister during the 1980s, appealed directly to Iran's all-powerful ruling clerics over the weekend to cancel the results of the election that showed the hard-line president with a landslide re-election. He wrote an appeal Sunday to the Guardian Council, a powerful 12-member body that's a pillar of Iran's theocracy. Mousavi also met Sunday with Khamenei.
Palmer reports that the Guardian Council said it would look into Mousavi's claims of fraud and report back within 10 days.
There were conflicting reports about the fraud investigation.
According to the Associated Press, state television reported Monday that Khamenei had ordered the powerful Guardian Council to investigate the claims of rampant election fraud.
Another major news agency's translation of the state TV report said Khamenei had merely warned Mousavi that he should proceed with his fraud complaints carefully, using "legal" means available to him. The differing reports could not be immediately reconciled.
Either way, the statements represent a nuanced turnaround for Iran's most powerful figure, who previously welcomed the election results. The focus of the opposition protester's angst had turned during the weekend to center on Khamenei.
Mousavi and his supporters have shown no sign of backing down against an expanding security clampdown - bringing their outrage to the streets for two straight days over claims that Ahmadinejad stole last week's election with vote rigging and fraud.
Ahmadinejad claims to have won by a landslide - with more than 60 percent of the vote. The results came as a surprise to many Iranians and external observers who watched days of raucous street rallies by Mousavi's mostly young supporters in the days before the vote.
Palmer reported that as those supporters learned from state media on Friday night, just hours after voting, that Ahmadinejad had won, their frustration boiled over into angry street protests. More than 100 were arrested as protesters clashed in the streets with police, who fought back with tear gas, rubber bullets and batons.
Ahmadinejad dismissed the demonstrations as " " and likened it to the intensity after a soccer game.
"Some believed they would win, and then they got angry," he said at a news conference on Sunday. "It has no legal credibility. It is like the passions after a soccer match. ... The margin between my votes and the others is too much and no one can question it."
"In Iran, the election was a real and free one," he told a room packed with Iranian and foreign media.
Ahmadinejad was scheduled to attend a regional summit in Russia Monday, but the visit was canceled at the last minute. The Iranian Embassy in Moscow said the president's visit had been postponed and could not say whether it would be rescheduled.
Mohsen Mirdamadi, an opposition strategist, was one of several people arrested during the weekend rioting, reported Palmer who had to hide in a shop with her cameraman during the protests to avoid beating and possible arrest at the hands of the police. Four days ago, Mirdamadi told CBS News there would be trouble if Mousavi lost.
"The main problem is that the people can't accept this is a real result," he told Palmer. "They won't believe it."
The re-election of Iran's hard-line president, meanwhile, signaled an for President Obama's hopes for ending Tehran's nuclear threat.
Mousavi has threatened to hold a sit-in protest at the mausoleum of the late Ayatollah Ruhollah Khomeini, founder of the 1979 Islamic Revolution, if authorities ban his followers from holding their rally. Such an act would place authorities in a difficult spot: embarrassed by a demonstration at the sprawling shrine south of Tehran, but possibly unwilling to risk clashes at the hallowed site.
A reformist activist close to Mousavi, Shahab Tabatabaei, said his supporters are determined to hold the rally despite the ministry's rejection.
Overnight, police and hard-line militia stormed the campus at the city's biggest university, ransacking dormitories and arresting dozens of students angry over what they say was mass election fraud.
The nighttime gathering of about 3,000 students at dormitories of Tehran University started with students chanting "Death to the dictator," but it quickly erupted into clashes as students threw rocks and Molotov cocktails at the police, who fought back with tear gas and rubber bullets, said a 25-year-old student at the university who witnessed the fighting. He would only give one name, Akbar, out of fears for his safety.
The students set a truck and other vehicles on fire and hurled stones and bricks at the police, he said. Hard-line militia volunteers loyal to the Revolutionary Guard stormed the dormitories, ransacking student rooms and smashing computers and furniture with axes and wooden sticks, Akbar said.
Before leaving around 4 a.m., the police took away memory cards and computer software material, Akbar said, adding that dozens of students were arrested.
He said many students suffered bruises, cuts and broken bones in the scuffling and that there was still smoldering garbage on the campus by midmorning but that the situation had calmed down.
"Many students are now leaving to go home to their families, they are scared," he said. "But others are staying. The police and militia say they will be back and arrest any students they see."
"I want to stay because they beat us and we won't retreat," he added.
One of Mousavi's Web sites, said a student protester was killed early Monday during clashes with plainclothes hard-liners in Shiraz, southern Iran. But there was no independent confirmation of the report. There also have been unconfirmed reports of unrest breaking out in other cities across Iran.