Police in Athens have clashed with protesters against austerity measures designed to save the Greek economy.
The march was peaceful but scuffles broke out between some demonstrators and police as the rally came to an end. Tear gas was fired.
The BBC reports a general strike is being held - the second in two weeks.
Greek airspace is closed to all flights. Trains and ferries are idle and archaeological sites have been shut.
Greece currently has a public deficit of 12.7%, more than four times higher than eurozone rules allow. The government has pledged to cut this to 8.7% this year. National debt is 300 billion euros.
The government is freezing public sector salaries, raising the average retirement age to 63 by 2015 and increasing taxes on petrol, alcohol and tobacco.