Since the fatal shooting of a 15-year-old in December, a wave of protests fuelled by anger at economic hardships and scandals has rocked Greece's ruling conservatives clinging to a one-seat parliamentary majority.

Hundreds of protesters on Thursday, chanting "state terrorism won't pass" and waving red flags, walked to parliament from the central Exarchia district, where police shot dead a teenager three months ago triggering the worst riots in decades.

After the protest, youths set garbage bins on fire and threw stones and firebombs at police causing damages to more than 20 cars and four shops in the centre of Athens. Riot police responded with tear gas.

"They threw stones and firebombs at police, who replied with ... tear gas," said a police official who declined to be named. "Shops and cars have been damaged".

Greece's public workers who staged a 24-hour nationwide strike this week protesting against low salaries and pension reforms have said the government's economic policy amid the global crisis only burdens the poor.