Local government workers were joined by Greek hotel staff in a protest against austerity on Wednesday.
The protesters marched through the capital, Athens, as part of two days of action against spending cuts to wages and pensions.
They form part of measures demanded of Greece by its international creditors to reduce its budget deficit.
Greek ministers have been in talks with the IMF, the EU and the European Central Bank since Sunday.
Athens must find a further 12 billion euros of cuts to tap the bailout money that the country needs to avoid bankruptcy.
Another demonstration is expected on Thursday, with doctors, teachers and other civil service staff set to take part.