Greece's main labor unions are holding another strike to protest a parliamentary vote on pension reforms that are part of government austerity measures.

Greek police say more than 10,000 people demonstrated in Athens Thursday, while about 5,000 others marched in the northern city of Thessaloniki.

Flights were canceled for most of the day, and public transportation throughout Greece halted.  Hospitals were open for emergencies only.

Greece's parliament planed to vote Thursday on cutting pension payments and raising the retirement age -- one of the conditions for receiving a $139 billion economic bailout from the European Union and International Monetary Fund.

Lawmakers approved pension reform in a preliminary vote Wednesday to gauge how much support the measure has.

Polls show many Greeks back pension reform and the government calls it an essential part of efforts to revitalize the devastated Greek economy.

Some information for this report was provided by AP and AFP.