Violent clashes on Tehran's streets

Police have beaten protesters and fired tear gas and water cannons at thousands who rallied in Tehran in open defiance of Iran's clerical government.

It is the most serious internal conflict since the 1979 Islamic Revolution.

Eyewitnesses described fierce clashes near Revolution Square after some 3,000 protesters, many wearing black, chanted "Death to the dictator" and "Death to dictatorship".

English-language state TV confirmed that police had used batons and other non-lethal weapons against what it called unauthorised demonstrations.

Witnesses said between 50 and 60 protesters were seriously beaten by police and pro-government militia and taken to Imam Khomeini hospital in central Tehran. People could be seen dragging away those injured by baton strikes.

Some protesters appeared to be fighting back, setting fire to militia members' motorcycles in streets near Freedom Square, witnesses said. Helicopters hovered over central Tehran. Ambulance sirens echoed through the streets and black smoke rose over the city.

Tehran University was cordoned off by police and militia while students inside the university chanted "death to the dictator", witnesses said. Police and militia barred people from entering Freedom Street, which runs from Freedom Square to Revolution Square, to prevent a massive gathering, the witnesses said.

Amateur video showed dozens of Iranians running down a street after police fired tear gas at them.

The English-language state channel said a blast at the Tehran shrine of Ayatollah Ruhollah Khomeini had killed one person and wounded two, but the report could not be independently confirmed due to government restrictions on independent reporting. The shrine is about 12 miles (20km) south of central Tehran.

Hundreds of thousands of supporters of reformist presidential candidate Mir Hossein Mousavi took to the streets for four consecutive days this week demanding the government cancel and rerun June 12 elections that ended with a declaration of overwhelming victory for hard-line president Mahmoud Ahmadinejad. Mr Mousavi says he won and that Mr Ahmadinejad stole the election through widespread fraud.