TEHRAN, June 16 (Xinhua) -- At least seven people have been killed at a mass rally held by tens of thousands of supporters of Iran's defeated reformist presidential candidate Mir-Hossein Mousavi, local English-language Press TV reported on Tuesday.

    The protesters were killed after they tried to attack a military post near Tehran's Azadi (Liberty) Square on Monday, the report said.

    Dozens of others were also wounded when protesters were trying to destroy public properties, the report added.

    Meanwhile, Press TV quoted Tehran's police as saying that security forces had arrested a number of "armed rioters" in connection with the recent clashes in Tehran.

    Press TV reported on Monday that gunshots were heard at the rally near Tehran's Azadi Square had been declared "illegal" by the authorities and people were running away.

    "There has been sporadic shooting out there," a reporter of Press TV said, "I can see people running here."

    The backers of Mousavi were "staging a calm and peaceful demonstration," the Press TV reporter said earlier, adding that the anti-riot police were calm but alert standing on the sides of the street observing the surge of the people.

    Iran's police chief Esmail Ahmadi-Moghaddam warned earlier on Monday that any illegal rally would be confronted in a legal way by the police.

    Mousavi addressed his fervent supporters by a mobile loudspeaker saying that he was ready to take part in any new election.

    On Saturday afternoon, Iran's Interior Minister Sadeq Mahsouli said that the incumbent President Mahmoud Ahmadinejad won 62.63 percent of the total ballots during Friday's vote, while Mousavi got 33.75 percent.

    After the official declaration, Mousavi protested "strongly" in a statement the "obvious" violations in Iran's presidential election.

    During a meeting with Mousavi on Sunday evening, Iran's Supreme Leader Ayatollah Ali Khamenei said he has ordered the Guardian Council to investigate the claims of fraud in the recent presidential election.

    He also told the former prime minister to pursue his appeal against the election result in a legal way.

    "You are different from those people (rioter protestors on the streets) and you are advised to keep manners and calmness," Khamenei said.