TEHERAN, Iran - June 15, 2009 - Gunmen have fired on opposition protesters at a massive march over alleged election fraud, killing at least one person.

An Associated Press photographer saw one person shot dead and several others who appeared seriously wounded in Teheran's Azadi Square. The shooting came from a compound for volunteer militia reportedly linked to Iran's powerful Revolutionary Guard.

The gunfire Monday came after more than 100,000 opponents of President Mahmoud Ahmadinejad streamed through Teheran. They were not challenged by security forces despite an earlier ban on rallies for reformist leader Mir Hossein Mousavi.

Disputes over alleged vote rigging in last week's elections have touched off days of rioting in Teheran.