ATHENS - STREET violence raged into a third week in Athens as protests sparked by the fatal shooting of a teenager fused with political tension hours from the Greek parliament's budget vote on Sunday.

Clashes between youths and police extended deep into the night after hundreds of people gathered late on Saturday in Athens' Exarchia district, at the site of the December 6 shooting of 15-year-old Alexis Grigoropoulos.

Protesters occupying the Athens Polytechnic university hurled firebombs and rocks at police who responded with tear gas, while police cars, a government building and banks were targeted in various parts of the capital, the port city of Piraeus and the island of Crete.

The unrest flared up after youths gathered on the spot where Grigoropoulos fell from a policeman's bullet, and where a makeshift shrine has since emerged.

Flowers and messages of support adorn the scene along with mock street signs bearing Grigoropoulos' name.

The officer who shot the teenager claims he fired into the air whilst under attack by youths, and has attributed the death to a bullet ricochet.

Investigators scoured the crime scene again early on Sunday in search for further clues, accompanied by lawyers for the Grigoropoulos family, the police officer and his partner who is also implicated in the murder.

'The crime scene search will help lead to conclusions but will not change our position,' said lawyer Dimitris Tsovolas who represented the victim.

The unrest later subsided as thousands of Athenians filled the city centre where protestors shared the streets in bizarre scenes this past week with throngs of Christmas shoppers.

The embattled right-wing government faced a fresh hurdle at midnight Sunday, when the budget - staunchly opposed by unions, and likely to trigger more protests if adopted - was to be put to a vote.

The budget makes provision for a two-percent deficit and 2.7-per cent growth - down from a current 3.1 per cent.

Prime Minister Costas Karamanlis has argued that the unrest is complicating efforts to reduce Greece's national debt, which this year stands at 93.9 per cent of GDP, one of the highest in Europe.

The conservative leader said last week that Greece expects to pay about 12 billion euros (S$23.34 billion) in 2009 to service its debt, amounting to over 19 per cent of its revenue and nearly five percent of GDP.

The depth of anti-government sentiment witnessed over the past fortnight has also cost the government dearly in opinion polls.

Socialist leader George Papandreou has overtaken Mr Karamanlis for the first time as the preferred man to be prime minister, pollsters Public Issue said in a survey published in the Kathimerini newspaper on Sunday.

Mr Karamanlis - whose government has a one-seat majority in parliament - has consistently shrugged off opposition calls to resign, announcing financial measures to support the business and tourism sectors hard-hit by the unrest.

Hundreds of shops and banks in Athens and elsewhere have sustained damage in street violence which nearly killed off the Christmas shopping season.

Again on Saturday, the giant Christmas tree on Athens' main square outside the parliament building was targeted by protesters. It was only replaced on Tuesday after the original was torched at the height of the unrest.

Later, a group threw a petrol bomb at a building housing the Greek credit database Tiresias SA which tracks the borrowing profile of millions of Greeks.

In a western suburb of Athens, demonstrators threw Molotov cocktails at the police academy and torched six police vehicles.

Groups of youths continued to set fire to garbage cans after dark in various parts of the city. -- AFP