Thousands of demonstrators in Greece have hurled firebombs and stones at riot police during renewed anti-government protests in Athens.
Police formed a cordon around parliament and fired teargas to disperse the crowd.
Hundreds of students clashed with police outside Athens university buildings, burning three cars and rubbish containers, while one group set fire to a security van.
Unions grounded flights and shut down public offices, in the lastest of the series of protests over the killing of a teenage boy by police.
A three-hour work stoppage by public workers halted all but emergency flights.
Urban transport services were frozen while doctors and teachers walked off the job.
Greece's worst disturbances in decades was triggered by the killing on 6 December of 15-year-old Alexandros Grigoropoulos.
The policeman who shot the teenager has been charged with murder and jailed pending trial, while his partner was charged as an accomplice. The officer said he fired a warning shot in self-defence against a group of youths.
A ballistic report said on Thursday the bullet ricocheted before killing the teenager but further investigation was needed to decide whether the policeman aimed or fired in the air.
The riots have caused hundreds of millions of euros in damage in Athens and have shaken a government with a fragile one-seat majority in parliament.
The protests have fed off anger at youth unemployment and the economic slowdown.
Greek Prime Minister Costas Karamanlis has announced tax breaks and other measures to boost flagging tourism, one of the main reasons for a slowing economy.