At least seven people were killed in a mass rally staged by supporters of defeated presidential candidate Mir-Hossein Moussavi in Tehran, state radio has reported.

According to the report, the protesters were killed after they tried to attack a military post near Tehran's Azadi Square on Monday.

Despite a ban by Interior Ministry, hundreds of thousands of Moussavi supporters staged a civil rally in to express their solidarity with the former premier, who suffered a crushing defeat in Friday's presidential election.

A Press TV correspondent reported Monday that as the protesters were beginning to disperse at sundown after a peaceful rally, unidentified gunmen fired shots into the crowd.

The shooters were reportedly not in uniform.

State radio said on Tuesday that the attackers were trying to vandalize public properties. Several people were also injured in the incident.

"Seven people were killed and 29 injured during the illegal rally on Monday," Tehran Governor General Morteza Tamaddon said on Tuesday.

At the rally, Moussavi told the crowd he was ready to take part in a new election.

The former premier has called on the Guardian Council, the body supervising the electoral process, to nullify the Friday election in which the incumbent President Mahmoud Ahmadinejad was declared victor by a landslide.