Tens of thousands of Iranians flooded the streets of Tehran yesterday to hear the country’s most influential powerbroker pronounce the Islamic Republic in crisis and as he called for the release of those arrested in recent pro-democracy demonstrations.

In a devastating attack on the regime, Ali Akbar Hashemi Rafsanjani, a leading cleric and former President, told a crowd at Tehran University that the Government had lost the people’s trust. Referring to the handling of last month’s disputed election, which President Ahmadinejad claims to have won, he said that the custodians of the Islamic Revolution had undermined its basic principles.

Hojatoleslam Rafsanjani condemned the brutal suppression of protests and called for the release of those detained during the post-election crackdown. The crowd acclaimed his address by chanting: “Death to the dictator” and “Leaders, give us arms”.

Police and pro-government Basij militiamen responded by firing teargas and using truncheons to break up the crowd, the largest street gathering in weeks. Mehdi Karoubi, one of the presidential candidates who claims that his votes were stolen last month, was assaulted by plainclothes militia.

At least 15 people were arrested, including the leading women’s rights campaigner and lawyer Shadi Sadr, who was beaten and dragged into a car in front of a crowd of her friends. “Shadi called me from an unknown location and said she was arrested by plainclothes officials who forcefully got her into a car,” her husband, Hossein Nilchian, said.

Hojatoleslam Rafsanjani’s sermon at the university, the cradle of the 1979 Islamic Revolution, came as a crucial opportunity to galvanise the embattled opposition, who believe that the election was stolen from the moderate challenger, Mir Hossein Mousavi.

Mr Mousavi’s attendance at yesterday’s sermon was his first official public appearance in weeks. He has been under virtual house arrest, his communications monitored, closest aides arrested and news outlets closed.

Hojatoleslam Rafsanjani, a key Mousavi sponsor, who heads the clerical council with the authority to remove the Supreme Leader, has spent the past few weeks canvassing the religious establishment in Qom to make such a move against him.

Only a month ago at the same venue, Ayatollah Ali Khamenei, the Supreme Leader of Iran, declared that the election debate was over and warned of consequences for those who questioned the victory of Mr Ahmadinejad, the conservative incumbent. Many within the clerical establishment saw his backing of one candidate as a betrayal of his position.

Hojatoleslam Rafsanjani couched his sermon yesterday with calls for unity but his challenge to the regime was unmistakable. “Today is a bitter day,” he said. “I hope with this sermon we can pass through this period of hardships that can be called a crisis.”

He warned Iran’s leaders not to ignore the will of the people — a key tenet of the revolution. “If the Islamic and Republican aspects of the revolution are not preserved, it means we have forgotten the principles of the revolution,” he said. “Our key issue is to return the trust which the people had and now to some extent is broken.”

Reminding worshippers of his close relationship with the late Ayatollah Khomeini, the founder of the Islamic Republic, he condemned the use of iron-fisted security forces to crush protests. “We knew what Imam Khomeini wanted. He didn’t want the use of terror or arms,” he said. Iran puts the official death toll at 20, although human rights activists believe that hundreds may have been killed during the protests.

Hojatoleslam Rafsanjani drew thunderous applause as, blinking back tears, he demanded the release of demonstrators. “It is not necessary that in this situation people be jailed. Let them join their families. We should not allow enemies to rebuke and ridicule us because of detentions. We should tolerate each other,” he said.

Outside the prayer hall protesters carrying green banners — the colour of Mr Mousavi’s election campaign — called on President Ahmadinejad to resign. Some evoked the slain martyrs of the protest movement, chanting:

“Sohrab is not dead, it is the Government that is finished” and “We are all one voice, we are all Neda”.

The regime had banned public rallies, which had largely died out since security forces launched the crackdown on the streets last month, making Friday prayers one of the few opportunities left to gather.

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