Supporters of defeated opposition candidate Mir Hossein Mousavi demonstrate in Tehran on Monday in protest of the re-election of President Mahmoud Ahmadinejad.

TEHRAN, Iran (AP)  Thousands of Iranians swarmed the streets of Tehran on Tuesday in rival demonstrations over the country's disputed presidential election, pushing a deep crisis into its fourth day despite a government attempt to placate the opposition by recounting a limited number of ballots. Iran 's supreme ruler drew a firm line against any threats to the regime, warning Iranians to unite behind the country's Islamic system as authorities imposed severe restrictions on independent media. After days of dramatic images of Iranians protesting the declaration of victory for hard-line President Mahmoud Ahmadinejad , the government said employees of foreign media could only cover events authorized and announced by the government. PHOTO GALLERY: Mousavi supporters protest, claim election fraud ELECTION: For U.S., 'doubts' linger as Iran roils Q&A: Iran election was called before tally was finished Supreme Leader Ayatollah Ali Khamenei made an extraordinary appeal in response to tensions over the disputed election, which has presented one of the gravest threats to Iran's complex blend of democracy and religious authority since the system emerged from the 1979 Islamic Revolution. "In the elections, voters had different tendencies, but they equally believe in the ruling system and support the Islamic Republic," Khamenei said at a meeting with representatives of the four presidential candidates. "Nobody should take any action that would create tension, and all have to explicitly say they are against tension and riots." A day after a massive opposition rally that ended in deadly clashes with pro-government militiamen, Iran's main electoral authority said it was prepared to conduct a limited recount of ballots at sites where candidates claim irregularities took place. Opposition candidate Mir Hossein Mousavi has called the election an "astonishing charade," demanding it be canceled and held again. His representative,cleric Ali Akbar Mohtashamipour, reiterated that demand Tuesday after a meeting of the Guardian Council, calling along with representatives of two other candidates for an independent investigation of voting irregularities. The Guardian Council is an unelected body of 12 clerics and Islamic law experts close to the supreme leader and seen as supportive of Ahmadinejad. Mousavi said Monday that he believes the council is not neutral and has already indicated support for Ahmadinejad. "If the whole people become aware, avoid violent measures and continue their civil confrontation with that, they will win. No power can stand up to people's will," Mohtashamipour said. "I do not think that the Guardian Council will have the courage to stand against people." A spokesman for the Guardian Council, Abbas Ali Kadkhodaei, did not rule out the possibility of canceling the results, saying that is within the council's powers, although nullifying an election would be an unprecedented step. In the afternoon, the government organized a large rally in Tehran, as if to demonstrate it also can bring people into the streets. Thousands waved Iranian flags and pictures of the supreme leader, thrusting their fists into the air and cheering as speakers denounced "rioters" and urged Iranians to accept the results showing Ahmadinejad was re-elected in a landslide Friday. "This nation will protect and defend its revolution in any way," Gholam Ali Haddad Adel, a prominent lawmaker and Ahmadinejad supporter, told the pro-government crowd in Vali Asr Square. He called on Mousavi's supporters to accept the results and press their complaints through legal means. "After all, in all elections there will be losers and winners, naturally," he said. "This should not cause a rift between the people." The appeal for unity failed to calm passions, and a large column of Mousavi supporters — some of them with green headbands and their faces masked against tear gas or to hide their identities — marched peacefully along a central avenue in north Tehran, according to amateur video. A witness told the Associated Press that the pro-Mousavi rally stretched more than a mile along Vali Asr avenue, from Vanak Square to the headquarters of Iranian state television. Security forces did not interfere, the witness said, and the protest lasted from about 5 p.m. to 8 p.m. Other witnesses told the AP that about 100 people continued the protest in front of state TV past 9:45 p.m. The witness spoke on condition of anonymity for fear of government reprisal. Mousavi appeared to be trying to harness the days of street rage into a more carefully directed campaign of civil disobedience. In a message on his website, he said he would not attend Tuesday's demonstration and urged his supporters not to resort to violence. The website said Mousavi and his supporters planned another large demonstration along the path of Monday's massive protest, for Wednesday afternoon. It said they have asked the Interior Ministry for permission but didn't say whether they got a response or if they would go ahead if rejected. Ahmadinejad, who has dismissed the unrest as little more than "passions after a soccer match," attended a summit meeting in Russia that was delayed a day by the unrest in Tehran. That allowed him to project an image as Iran's rightful president, welcomed by other world leaders. In Washington, President Obama expressed "deep concerns" about the legitimacy of the election and post-voting crackdowns but declined to term Ahmadinejad's re-election a fraud. "I do believe that something has happened in Iran," with Iranians more willing to question the government's "antagonistic postures" toward the world, Obama said. "There are people who want to see greater openness, greater debate, greater democracy." After images were shown around the world of Monday's mass protests and violence, authorities said foreign media, including Iranian employees, could only work from their offices, conduct telephone interviews and monitor official sources such as state television. The rules prevent news outlets, including the Associated Press, from sending independent photos or video of street protests or rallies. Also Tuesday, foreign reporters in Iran to cover last week's elections began leaving the country. Iranian officials said they will not extend their visas. At least 10 Iranian journalists have been arrested since the election, "and we are very worried about them, we don't know where they have been detained," Jean-Francois Julliard, secretary general of Reporters Without Borders told AP Television News in Paris. He added that some people who took pictures with cellphones also were arrested. A website run by former vice president Mohammad Ali Abtahi said the oppositionist had been arrested. Saeed Hajjarian, a prominent oppositionist, also has been detained, Hajjarian's wife, Vajiheh Masousi, told the AP. Hajjarian is a close aide of former president Mohammad Khatami . Iranian state radio said seven people were killed in Monday's protests — the first confirmation of deaths from the demonstrations that started Saturday after the election results were announced. It said people were killed during an "unauthorized gathering" at a mass rally after protesters "tried to attack a military location." Copyright 2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed. Guidelines: You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. You share in the USA TODAY community, so please keep your comments smart and civil. Don't attack other readers personally, and keep your language decent. Use the "Report Abuse" button to make a difference. Read more