About 15,000 protesters are taking part in anti-government rallies before a visit to Greece by bailout inspectors and plans by the left-wing government to impose more austerity measures after years of economic hardship.

The protesters — beating drums, waving black flags and holding helium balloons bearing anti-government slogans — marched through the center of Greece's second-largest city, Thessaloniki, where Prime Minister Alexis Tsipras was due to speak on the state of the nation's economy.

Greece has spent most of the last eight years in recession and is currently going through its third major round of austerity measures tied to international bailout packages.