ATHENS - Clashes with anti-riot forces ended a series of rallies organized by student unions, left-wing parties and anti-establishment groups in the center of Athens on Wednesday to mark the ninth anniversary of the fatal police shooting of a teenager in 2008.

Hooded protesters, after setting fire to garbage containers, threw scores of petrol bombs, bricks and flares at police in riot gear who responded with tear gas and stun grenades.

Most scuffles took place at the district of Exarchia near the spot where the 15-year-old high school student Alexandros Grigoropoulos was shot dead on Dec. 6, 2008 by a policeman who was convicted later to life imprisonment.

Grigoropoulos' death was followed by a string of violent clashes across Greece for two weeks in protest of police violence. The anniversary has been marred by violent incidents every year.

An earlier march by students and high-school pupils in Athens on Wednesday was disrupted by violent clashes by small groups of youths. Greek riot police responded with limited use of tear gas in the center of the capital to disperse them.

Some 3,000 officers were deployed across the city center of Athens to monitor the protests.

Violence also broke out in Thessaloniki in northern Greece where demonstrators threw petrol bombs at police.

Greek police were on high alert with tight security measures ahead of the official visit by Turkish President Recep Tayyip Erdogan in Athens on Thursday.

Authorities banned all protest rallies and demonstrations in central Athens from 6 am on Thursday to 12 pm on Friday.

The metro station "Syntagma" is to remain closed all day on Thursday, while, the traffic in Athens will be temporarily interrupted and there will be changes in buses and trolley's itineraries following police directions.