A group of hooded youths armed with crowbars and sledgehammers yesterday vandalised shop fronts, banks and cars in the affluent Athens district of Kolonaki, police and witnesses said.

Midday shoppers were stunned to see around 50 youths smashing windows as they ran towards the bohemian district of Exarcheia, the centre of serious unrest last December over the fatal shooting of a teenage boy by police.

"It all happened very quickly," a witness told private Flash radio.

"They told us to leave the area and started smashing windows with sledgehammers as they ran down the street," he added.

"We thought it was a robbery at first," a shop attendant said.

"All our windows are smashed. I was forced to duck for cover along with my customers," she added.

Nobody was apparently injured but the youths smashed and damaged the windows of at least four banks, around 50 stores and cafes and 10 cars parked on at least two streets, AFP reporters said.

They left behind leaflets demanding the release of a young self-styled anarchist, the son of a leading leftist politician, who was arrested in a 2007 bank robbery and has been detained since.

The youths subsequently sought refuge in the nearby Athens law faculty which is covered by strict regulations that limit police entry into university buildings.

Attacks on property in Athens and the northern city of Thessaloniki have multiplied following the death of 15-year-old Alexis Grigoropoulos last December, with experts noting a dangerous wave of radicalisation among a section of the country's youth.

Several businesses in Kolonaki, one of Athens' best-guarded areas and home to several embassies and the homes and offices of government officials, were also vandalised at the time.