A 24-hour general strike brought Greece to a standstill on Wednesday amid continued protests against government spending cuts.
Athens has agreed on tougher austerity measures with its international lenders: the so-called troika of the European Central Bank, the European Commission and the IMF.
Public sector cuts and a wave of privatisations form part of Greek efforts to trim its budget deficit and receive the next slice of emergency funding of 8 billion euros.
Earlier this week, the Greek government said it would miss its deficit target of 7.5 percent this year, saying it will stand at 8.5 percent.
The strike has already brought Greek public transport to a halt with rail, bus and metro workers all taking part in the industrial action.
For the first time this year, Greek air traffic controllers have joined the strike.
A spokeswoman for Athens airport said more than 400 domestic and international flights have already been cancelled.