Tehran, July 17 (DPA) Iranian police several times used teargas against thousands of supporters of opposition leader Mir-Hossein Moussavi during the Friday prayers ceremony in central Tehran, witnesses said.

Several protesters were arrested by police in front of the Tehran University where the prayers were held, the witnesses said.

Hundreds of thousands of opposition supporters rushed to the venue in central Tehran, but only thousands reached the front gate of the Tehran University.

Earlier, former Iranian president Akbar Hashemi-Rafsanjani called for an 'open debate' on the recent controversial election which saw President Mahmoud Ahmadinejad retain power.

He also called on the authorities in Friday prayers address to release opposition figures who have been imprisoned during a major crackdown on protesters which followed the election June 12.

A radius of more than three kilometres was filled with people surging towards the university, witnesses said.

Most were unable to get anywhere near the prayer venue, where large numbers of police and volunteer security forces formed a tight security cordon.

Witnesses said thousands of mainly Moussavi supporters, however, gathered in front of Tehran University wearing green masks. Most of the women wore green headscarves. Green is the colour for Moussavi's opposition movement.

Rafsanjani began the speech with an appeal for calm. 'Let us use the occasion to create a better future for our country,' he told the crowd in his first public appearance since the election.