Greek workers clash with police during austerity protest
As protesters gathered in Athens, public services were hit and some transport services ground to a halt.
Greek workers are staging their first general strike against austerity since Alexis Tsipras's left-wing Syriza government came to power in January.
Brief clashes were reported in Athens, as youths broke away from the main protest near parliament.
The main unions appealed for members to walk out against the terms of Greece's third eurozone bailout. The government agreed to push through tax rises and spending cuts in return for €86 billion in rescue loans.
As protesters gathered in Athens, public services were hit and some transport services ground to a halt.
MPs have already voted to raise the retirement age and get rid of most early retirement benefits, and reduced rates of sales tax on some of the big Greek islands have been scrapped.
But the main civil servants' union ADEDY and the GSEE private sector union objected to proposals to scale back supplementary pensions and merge pension funds. They were joined by communist-affiliated union PAME.
In Athens, reports said dozens of young people dressed in black threw petrol bombs and broke shop windows near the main parliamentary building in Syntagma Square.
Small fires were also seen at the entrance to the Bank of Greece headquarters. Police then responded with tear gas.
Metro, ferry and suburban rail services were shut down, schools were closed and hospitals had only emergency staff levels. Buses and trolley buses were providing limited services.
Museums and archaeological sites were shut and news bulletins, newspapers and websites were disrupted because journalists had walked out.