Greece on Sunday braced for a second week of protests over the death of a teenager by a police bullet, as demonstrators staged fresh violence moments after vigils were held for the schoolboy victim.

Around 100 hooded youths firebombed a station next to Athens' Exarchia district late Saturday, where 15-year-old Alexis Grigoropoulos died from a police bullet a week ago.

At about the same time, similar numbers in Thessaloniki, Greece's second city, vandalised a gymnasium before holing up behind university walls.

About 200 youths stationed themselves before parliament in Athens late on Saturday, as security forces ringed them and then chased them away.

A police source said demonstrators hurled Molotov cocktails and set off fires at three banks near the Athens Polytechnic from where self-styled anarchist leaders say they are planning a sustained campaign.

An office of the environment ministry and public property were also targeted, with bins set ablaze across the area, police added.

The fresh outbreak of hostilities followed largely silent ceremonies marking the moment Grigoropoulos was killed.

Greece has been gripped over the past eight days by a deep-rooted protest movement which has succeeded in uniting mainstream and radical youth and that the opposition socialists are seizing upon to press for fresh elections.

The lull during peaceful rallies led by several hundred mourners holding lit candles and posting messages on a wall by the spot where the boy fell, had followed overnight attacks on banks and more tense stand-offs with police.

Some 2000 demonstrators ? mainly Polytechnic students ? had earlier on Saturday squared up to police outside the Greek parliament on the eighth day of their dogged challenge.

They brandished a large banner which read: "06/12/08, Alexis Grigoropoulos, I won't forget."

Student pamphlets also announced rallies planned in front of the Athens police headquarters on Monday and back at parliament square on Thursday, when school pupils and teachers are expected to support the protests.

About 2000 youths also marched peacefully in Thessaloniki on Saturday afternoon, while later some 300 gathered silently around the city's emblematic White Tower monument.

Police have identified five banks attacked with gas canisters in Athens overnight Friday. A local party office of the ruling conservative party was also targeted.

The deeply held anger which has emerged within the lower end of the 15-24 age group ? a quarter of whom nationally remain unemployed ? could fester for months, if past Greek unrest is taken as a guide.

Greek Prime Minister Costas Karamanlis has meanwhile dismissed opposition calls to quit saying: "At this time the country faces a serious financial crisis... a steady hand on the helm is needed to deal with it.

"That is my concern, that is the priority of the government, not scenarios about elections and successions.

The offices of lawyer Alexis Kougias, representing two policemen charged over Grigoropoulos's death, have already been trashed, while elsewhere in Europe, demonstrators have blocked traffic on the Champs-Elysees in Paris with hundreds marching in Berlin to show solidarity.

The officer who shot Grigoropoulos says he killed the boy by accident out of self defence due to a bullet ricochet. A ballistics report, said to confirm that the handgun was not pointed at him, has yet to be released.