Big crowd turns out for pro-Mousavi rally in Tehran

TEHRAN (Reuters) - Tens of thousands of supporters of defeated presidential candidate Mirhossein Mousavi gathered for a rally in downtown Tehran on Monday, defying an Interior Ministry ban, a Reuters witness said.

"The street is fully packed," the witness said, adding the crowd was waiting for Mousavi and other pro-reform leaders who back his call for the annulment of the official result of Friday's election, which showed President Mahmoud Ahmadinejad had won.

Wearing Mousavi's green campaign colors and photographs of him, they chanted: "Mousavi take back our votes."

Several kilometers of a central Tehran thoroughfare were packed with people taking part in the rally, the witness said.

"Where are the 63 percent who voted for Ahmadinejad?" they chanted, referring to his official election tally.

"If Ahmadinejad remains president we will protest every day," they shouted. "We fight, we die, we will not accept this vote rigging," was another chant in the crowd.

As a police helicopter flew overhead, the crowd booed.

Ahmadinejad and Interior Ministry officials have dismissed allegations the vote was rigged. The president has called the election "free and healthy."

(Reporting by Parisa Hafezi; writing by Fredrik Dahl; editing by Dominic Evans)