Tensions are mounting in the Iranian capital Tehran as supporters of defeated reformist presidential candidate Mir Hossein Mousavi carry out a sixth day of demonstrations. Mousavi supporters are protesting last Friday's election results and mourning the deaths of at least seven people killed in fighting with pro-government militia since Monday. Human rights groups say that up to 500 activists, politicians, journalists and students may have been detained in the post-election protests.

Tens of thousands of supporters of defeated Iranian presidential candidate Mir Hossein Mousavi have packed Tehran's Imam Khomeini Square, according to eyewitness reports. They are mourning victims of earlier unrest this week and to protest alleged fraud during Iran's presidential election, which according to government figures, President Mahmoud Ahmadinejad won with 63 percent of the vote.

Mr. Mousavi reportedly joined the massive rally, according to his Facebook Internet support group, addressing the crowd briefly via loudspeaker.

Eyewitness reports say that he told the crowd that he had come "to defend the rights of the nation and to restore the pride, dignity and future of its people." He added that it is his goal to "bring freedom, dignity and hope" to the country.

A large part of the crowd, dressed mostly in black, unfurled a giant green cloth meant to represent Mousavi's campaign colors and the unity of Iran's people.

Other reports indicated that Iranian military helicopters circled overhead as demonstrators gathered, but did not intervene.

Multiple reports on Facebook and Mr. Mousavi's website indicated that Iranian troops were also watching benignly as protesters demonstrated, without intervening.

Several Iran analysts have said that Mousavi organizers have adopted the tactics of the late founder of the Islamic Republic, Ayatollah Ruhollah Khomeini, by placing flowers in soldier's guns to win them over.

A spokesman for Iran's influential Guardian Council, which is investigating 646 charges of election fraud, told the country's official Press TV that the group will meet with the three defeated candidates to examine their complaints more fully."

Press TV also indicated that the country's Supreme Leader Ayatollah Ali Khamenei would lead Friday prayers and "has invited the candidates to join in."

At least three different videos, posted on the Internet, show a thick sea of demonstrators on a Tehran boulevard, marching to a pro-Mousavi rally Wednesday.

Demonstrators could be heard chanting "allahu akbar," and "death to the dictator," in reference to incumbent President Mahmoud Ahmedinejad, who was declared the winner of Friday's election with 63 percent of the vote to Mr. Mousavi's 36 percent.

One photo showed a demonstrator carrying a sign with the message "empty hands always win over bullets."

A video, reportedly from the Iranian city of Shiraz, also showed hundreds of mostly young people marching down a wide boulevard and shouting "down with the dictator," and "Ahmedinejad be ashamed and leave the country."

Iranian analyst Mehrdad Khonsari with the London-based Center for Arab and Iranian Studies says that the fate of the popular protest movement is in the hands of Supreme Leader Ayatollah Ali Khamenei.

"I think certainly the protests have not petered out like it was originally anticipated," Khonsari said. "And it looks as though there is still a great deal of life still left in the process. The demonstrators have not given up in any sense. Obviously, how this process continues depends very much on what the Supreme Leader has to say, tomorrow [during Friday prayers]. It is obvious that everyone within the ruling establishment in Iran is trying to arrive at some sort of compromise to avert the continuation of this standoff. But if the Supreme Leader does not consent to the holding of fresh elections or holding some kind of a runoff election between Mousavi and Ahmedinejad, it is doubtful whether the demonstrators are going to be appeased to such an extent that they would call off their protests."

Meanwhile, Amnesty International and the New York-based International Campaign for Human Rights say that they have unconfirmed reports that hundreds of Iranian activists, politicians, journalists and students have been arbitrarily arrested by the government.

Iranian state television quoted Iran's Police Minister as saying that "15 agitators who were stirring up violence in Tehran" were arrested on Wednesday.

Watch video of the protests obtained by VOA's Persian News Network.
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