Simmering political tensions boiled over on Thursday when Iranian police fired tear gas and used batons to disperse demonstrators who had come to the grave of a woman who has become the figurehead for the anti-government movement.
Thousands of demonstrators had gathered at the cemetery where Neda Agha Soltan is buried. Soltan's graphic shooting death on June 20 during a Tehran protest was captured on video and released on the Internet.
The group had come for a silent memorial to honour victims of post-election violence in Iran. Opposition leader Mir Hossein Mousavi had planned to attend the gathering, but was blocked by police.
Amateur video purported to be from the event, showed thousands of demonstrators marching through the cemetery, some of them wearing green shirts in support of Mousavi's reformist movement.
Many in the group chanted "Neda is alive, Ahmadinejad is dead," referring to President Mahmoud Ahmadinejad, whom many believe won the election through fraudulent means.
Another demonstration took place at the main Masalla mosque in central Iran, with security forces stationed close by.
When Mousavi himself arrived at the site, hoping to join in the demonstration, he was instantly surrounded by hundreds of police who forced him to leave the cemetery.
During the clash, The Associated Press reports, his supporters chanted "yaa Hossein, Mir Hossein," comparing him to the grandson of the Prophet Muhammad.
And after he was forced to leave, supporters stayed at the site chanting "death to the dictator" in reference to Ahmadinejad -- with the crowd swelling into the thousands.
The violence began when a political ally of Mousavi tried to make a speech. Police reportedly rushed the site, fired tear gas and used batons to break up the crowd.
The purpose of the rally was to build momentum for the opposition movement, which has been subject to a seven-week police and military crackdown on media and public gatherings.
The violent police intervention, intended to break up the event, may have actually helped the protesters' and provided new fuel for the movement.
The memorial marked the end of the 40-day Islamic mourning period for 10 people who were killed in the protests on June 20 that also left Soltan dead.
According to the official count, a total of 30 people were killed in the security crackdown following the election. But human rights groups say the number is more like 100.
Hundreds of people were arrested in the crackdown, with many still imprisoned. There have been widespread allegations that many of those imprisoned are being tortured and even killed, triggering tough criticism from clerics and people on both sides of the political spectrum.
