Witnesses described fierce clashes after some 3,000 protesters, many wearing black, chanted "Death to the dictator!" and "Death to dictatorship!" near Revolution Square in downtown Tehran. Police fired tear gas, water cannons and guns but it was not clear if they were firing live ammunition.

Some protesters appeared to be fighting back, setting fire to militia members' motorcycles, witnesses said. There were no immediate confirmed reports of fatalities and the head of Iran's police said his men had been ordered to act with restraint.