Police clashed with supporters of Iran's opposition leader Mirhossein Mousavi in Tehran Wednesday when a rally marking the 30th anniversary of the storming of the US embassy turned violent. Reformist website Mowjcamp said police opened fire on protesters at Haft-e Tir square, but there was no independent confirmation of the report. “Some people were injured,” Mowjcamp said, reporting other protests in the cities of Shiraz and Rasht. Iran's Revolutionary Guards and their allied Basij militia had warned the opposition not to try to hijack an annual anti-US rally to revive protests against the clerical establishment after June's disputed presidential election. “Police clashed with hundreds of protesters. They were chanting: ‘Death to dictators'. Police used batons to disperse them,” a witness said. People traditionally chant, “Death to America” at the annual state-organized rally. The crackdown showed no compromise from the leadership, underlined by Supreme Leader Ayatollah Ali Khamenei's recent comment that it was a crime to question the June 12 vote which secured the reelection of President Mahmoud Ahmadinejad. Defeated presidential candidates Mousavi and Mehdi Karoubi, who are committed to reform, had urged supporters to take to the streets Wednesday to protest against the government despite warnings from the security forces about “illegal gatherings”. Karoubi, who joined the protests Wednesday, was attacked by plainclothes officers, his website Tagheer said. “One of his bodyguards was hospitalised.” There were no further details. Police fired teargas at the crowd and arrested at least five protesters, one witness said. Mobile phone networks were shut down to try to prevent protesters from organising while Basij militia on motorbikes drove at crowds and used batons. “There are hundreds, chanting ‘God is greatest'. Police and Basij militia are outnumbering the protesters,” one witness said. “Hundreds of police, riot police, Basij militia and plainclothes officers are in the main squares,” another said.