View a slideshow of eyewitness accounts of Tehran protests

Thousands of Iranians have staged another rally against the re-election of President Mahmoud Ahmadinejad, defying a government ban on protests.  
 

Hundreds of thousands of Iranian supporters of defeated reformist presidential candidate Mir Hossein Mousavi demonstrate in Tehran, 15 Jun 2009

Tens of thousands of supporters of pro-reform leader Mir Hossein Mousavi took to the streets of Tehran for a third day to protest the election results that declared President Mahmoud Ahmadinejad the winner.

The march came hours after of Iran's supreme leader, Ayatollah Ali Khamenei, ordered an examination into Mr. Mousavi's claims of vote rigging. 

President Ahmadinejad has faced demonstrations and riots since Saturday, when officials announced his landslide victory in Friday's election.  Following two days of unrest, the interior ministry said anyone disrupting public security would be dealt with according to the law.

Mr. Ahmadinejad has dismissed the protesters' claims, saying the election was free and fair.  Defeated candidate Mousavi urged calm in a message on his Internet Web site.

Thousands of his supporters continue to post hundreds of messages to a Mousavi support group on the Facebook website.  The site is being blocked inside Iran, but many Iranians are still able to access it via proxy servers.
 
Dozens of pictures of police brutality were posted, including a young man drenched in blood, and a black-clad riot policeman pounding demonstrators who had fallen to the ground."
 

Hundreds of Iranian presidential candidate Mir Hossein Mousavi's supporters attend a protest, in front of the Iranian Consulate, in Dubai, 15 Jun 2009

A song to protest the government crackdown, called "Be Free Iran," is also gaining popularity among young Iranian demonstrators, who are exchanging it via the Internet, to express support for the burgeoning protest movement.
 
"This is the start of a brand new revolution," wrote one young man who identified himself as Reza on the Mousavi Web site. "It is not going to stop."

"Honk your car horns," wrote a young woman named Rubina, "and stop near government buildings [to protest]"
 
Despite what appears to be the growing momentum of popular discontent, Tel Aviv-based Iran analyst Meir Javedanfar of the MEEPAS center says close scrutiny is needed to determine where the situation in Iran is heading.
 
"I think it depends on three factors: Number one, how senior are the people who are going to become involved in the demonstrating; the more senior they are, the more people will become encouraged," Javedanfar said.  "Number two; if the demonstrations spread to other cities. I think the more cities that become involved, the more the leadership will take notice.  And, also, number three; the duration of this.  If this continues for another two weeks, I think the Supreme Leader, Ayatollah Ali Khamenei, will have a serious situation on his hands.  Until then, we should sit down and watch the developments and see what the Supreme Leader says."

Dozens of reformist political leaders are reportedly under house arrest, but some analysts say dissension within the government appears to be causing confusion and preventing a full-scale crackdown.