Masses of pro-reform demonstrators flood streets of Tehran

Tens of thousands of supporters of Iranian pro-reform leader Mir Hossein Mousavi streamed through the center of Tehran Monday in a boisterous protest against election results that declared President Mamoud Ahmadinejad the winner.

The crowd - many wearing the trademark green color of Mousavi's campaign -headed toward the capital's huge Freedom Square in the largest display of opposition unity since Friday's elections ended with Mousavi claiming widespread fraud.

There was no sign of violence or challenges from security forces. Anti-riot stood by with their helmets off and shields at their sides.

The march Monday came hours after Iran's supreme leader, Ayatollah Ali Khamenei, ordered a probe into Mousavi's claims of vote rigging. But it was unclear how the investigation would proceed.

The march came hours of Iran's supreme leader, Ayatollah Ali Khamenei, ordered a probe into Mousavi's claims of vote rigging. But it was unclear how the investigation would proceed.