Gunfire was reported Monday night at a rally in Tehran in support of reformist candidate Mir-Hossein Moussavi. Eyewitnesses reported that at least one person was killed, and several others were wounded.
The shooting has been blamed on a militia loyal to current Iranian President Mahmoud Ahmadinejad.
Moussavi's supporters took to the streets on Monday despite the government's refusal to grant them a protest permit. Hundreds of thousands took part in a massive rally in Tehran.
Prior to the shooting, Moussavi arrived at the rally to address the crowd in his first public appearance since the elections.
Ahmadinejad's opponents have accused the government of rigging last week's elections. According to the official results, Ahmadinejad won in a landslide. However, Moussavi claims that he was the rightful winner of the elections.
European Union leaders expressed concern over the alleged voting fraud and the subsequent government crackdown on reformists. German Foreign Minister Frank-Walter Steinmeier called the actions of Iranian police “completely unacceptable,” while British Prime Minister Gordon Brown warned Iran that its response to protestors “will have implications for Iran's relationships with the rest of the world in the future.”
Riots worsened on Monday night despite a statement from Ayatollah Ali Khamenei, who called for an official investigation of the elections process.