A worker smashes a window of a burned building in central Athens. (AP)
Police in Greece say a government administrative building was severely damaged in an arson attack.
The offices near central Athens used by the government's Public Sector Reform Ministry were attacked early on Monday.
Police said small cooking gas canisters were used to make the device, adding that there was no warning or immediate claim of responsibility.
Arson and minor bomb attacks are common in Athens, and mostly carried out by anarchist groups who typically target banks and government property.
Amid a financial crisis in the country, Greeks have been hard-hit by a series of cuts to their salaries and pensions which is meant to reign in government spending and reignite the country's ailing economy.
The burning of the Reform Ministry building follows an attack on a police officer on Saturday.
Greek protesters, marching in memory of a man who killed himself over financial woes that he blamed on the government, attacked a policeman in Athens leaving him bloodied and stealing his bullet-proof vest.
The demonstrators marched after a memorial service for Dimitris Christoulas, 77, a retired pharmacist who shot himself Wednesday in the Greek capital's Syntagma Square.
He left a note blaming politicians for his money problems and calling on "young people" to kill their elected leaders.
His death has further galvanised Greeks angry over their leaders' implementation of tough austerity measures that are aimed at bringing the country out of its fiscal crisis but which have caused hardships for many ordinary citizens.
Greece's economy is now also heavily dependent on international loans.