Witnesses Report Fierce Clashes In Tehran

Last Updated 9:51 a.m. ET.

Witnesses said police fired tear gas and water cannons at thousands of protesters who rallied in Tehran Saturday in open defiance of Iran's clerical government, sharply escalating the most serious internal conflict since the 1979 Islamic Revolution.

CBS News correspondent Elizabeth Palmer, one of the last remaining Western journalists in Tehran, reports that people gathering in Tehran's center have been met by a heavy police presence.

Supporters of opposition leader Mir Hossein Mousavi are rallying in Tehran in open defiance of the country's supreme leader who threatened harsh action if protestors take to the streets again demanding a new presidential election.

Eyewitnesses described fierce clashes near Revolution Square in central Tehran after some 3,000 protesters chanted "Death to the dictator!" and "Death to dictatorship!" Police responded with tear gas and water cannons, the witnesses said.

English-language state TV also reported a blast at the Tehran shrine of Ayatollah Ruhollah Khomeini had killed one person and wounded several others, but the report could not be independently confirmed due to government restrictions on independent reporting.

IranWatch: Track the latest on the Iran election upheaval

Supreme Leader Ayatollah Ali Khamenei warned opposition leaders on Friday to end street protests or be held responsible for any "bloodshed and chaos" to come.

Eyewitnesses contacted by The Associated Press said thousands of police and plainclothes militia members filled the streets Saturday to prevent rallies. Fire trucks took up positions in Revolution Square and riot police surrounded Tehran University, the site of recent clashes between protesters and security forces, one witness said.

Palmer termed the crowds of protestors as "large" but impossible to put a figure on it. Traffic jams made movement difficult, and Palmer - who passed groups of people moving towards the site of a planned protest today - said it would be easy to be trapped.

Mousavi had received another stern warning Saturday not to encourage his supporters to take to the streets a day after Khamenei sought to end the deepening election crisis by effectively declaring President Mahmoud Ahmadinejad the winner and threatening those who continue to protest.

Khamenei ordered opposition leaders on Friday to end street protests or be held responsible for any "bloodshed and chaos" to come.

Web sites run by supporters of Mousavi called for street protests at 4 p.m. local time (7:30 a.m. ET) but the candidate himself issued no public statement.

Fire trucks took up positions in Revolution Square, the site of the planned gathering, and riot police surrounded Tehran University, the site of recent clashes between protesters and security forces, one witness said.

Iran's Interior Ministry also reiterated the warning to Mousavi on Saturday, saying he would "be held responsible for the consequences of any illegal gatherings." The ministry also accused the 67-year-old former prime minister of supporting protests that "have lead to the disruption of security and public order," State Security Council secretary, Abbas Mohtaj, said in a statement on the ministry's Web site.

A top Iran police official, Ahmad Reza Radan, warned Mousavi Saturday that if people take to the streets, "their leaders will be arrested."

The warnings place Mousavi at a pivotal moment. He can either back down or risk a crushing response from police and the forces at Khamenei's disposal - the powerful Revolutionary Guard and their volunteer citizen militia, the basij. One of Mousavi's Web site's said he planned to issue a statement "soon." It did not elaborate.

"If anything, there is even less traffic than usual. Everybody is wondering what the opposition is going to do after the Supreme Leader's warning yesterday that the protests must stop."

The police have warned that any protest will be illegal and will be dealt with determination, Palmer said.

A top Iran police official, Ahmad Reza Radan, warned Mousavi Saturday that if people take to the streets, "their leaders will be arrested."

The still-defiant opposition did not come to to a meeting with Iran's senior clerical body, the Guardian Council, which was called to try and find some solution to this impasse, some way of dealing with their complaints of election fraud.

There have been conflicting messages on whether or not there is going to be a march Saturday. Zahra Rahnavard, the wife of Mousavi, said online this morning that she would be there, so by implication there will be a march.

There also are questions about Mousavi's ability to control his own followers, many who are waiting for a clear response to Khamenei's edict on Friday before Saturday's planned rally.

Mousavi, who accuses the government of widespread voter fraud in the June 12 election, and the two other candidates who ran against Ahmadinejad were slated to meet with Iran's Guardian Council on Saturday. The council, an unelected body of 12 clerics and Islamic law experts close to Khamenei, investigates voter fraud claims.

But state-run Press TV said Mousavi, and the reformist candidate Mahdi Karroubi did not attend. There was no other details.

The council has said it was prepared to conduct a limited recount of ballots at sites where candidates claim irregularities. It not clear, however, if they have initiated any investigations.

Hundreds of thousands of Mousavi supporters have flooded Tehran streets during several massive marches earlier this week that recall the scale of protests during the 1979 Islamic Revolution.

In a first sign of possible resistance to Khamenei's orders came shortly after nightfall in Tehran Friday. Cries of "Death to the dictator!" and "Allahu akbar" - "God is great" - rang from rooftops in what's become a nightly ritual of opposition unity.

Since the June 12 election, Mousavi has become the figurehead for a broad collection of demonstrators - from the most liberal-leaning reformists to religious conservatives. Some could be prepared to take their protests to the limit, but many others have no interest in an all-out mutiny against the country's Islamic system.

Khamenei was blunt Friday about what a wider fight would bring - warning those who "want to ignore the law or break the law" will face the consequences.

Police clashed with protesters in running battles around Tehran immediately after the election and the basij militia had a reported role in attacks at the university. Gunfire from a basij compound in Tehran also left at least seven people dead Monday.

But the full force of the police and Revolutionary Guard has remained in check. And this was Khamenei's implicit message since the Guard and the vast volunteer militia force it controls is under direct command of the ruling clerics.

A spokesman for Mousavi said Friday the opposition leader was not under arrest but was not allowed to speak to journalists or stand at a microphone at rallies. Iranian filmmaker Mohsen Makhmalbaf told the AP from Paris it's even becoming difficult to reach people close to Mousavi. He said he has not heard from Mousavi's camp since Khamenei's address.

Iranian authorities have placed strict limits on the ability of foreign media to cover recent events, banning reporting from the street and allowing only phone interviews and information from officials sources such as state TV.

British Prime Minister Gordon Brown and other European Union leaders expressed dismay over the threat of a crackdown.

Both houses of the U.S. Congress approved a resolution condemning "the ongoing violence" by the Iranian government and its suppression of the Internet and cell phones.

In an interview taped Friday with CBS, Obama said he is very concerned by the "tenor and tone" of Khamenei's comments. He also said that how Iran's leaders "approach and deal with people who are, through peaceful means, trying to be heard" will signal "what Iran is and is not."

The crowds in Tehran and elsewhere have been able to organize despite a government clampdown on the Internet and cell phones. The government has blocked certain Web sites, such as BBC Farsi, Facebook, Twitter and several pro-Mousavi sites that are conduits for Iranians to tell the world about protests and violence.

Text messaging has not been working in Iran since last week, and cell phone service in Tehran is frequently down.