Protesters clash with police in Athens

A demonstrator throws a stone at riot police during a protest Photograph: Aris Messinis/guardian.co.uk

A riot policeman's clothing catches fire after demonstrators threw petrol bombs at them, as violence erupted in Athens Photograph: Dimitri Messinis/guardian.co.uk

Riot policemen try to drag away a demonstrator, and one of them hits him on the head trying to subdue him Photograph: Dimitri Messinis/guardian.co.uk

A demonstrator shows a finger to riot police during a protest in Athens Photograph: Aris Messinis/guardian.co.uk

Police detain a demonstrator in central Athens Photograph: Aris Messinis/guardian.co.uk

Riot policemen detain a protester during clashes Photograph: Simela Pantzartzi/guardian.co.uk

Youths clash with police in Athens during a massive demonstration Photograph: Louisa Gouliamaki/guardian.co.uk

An injured protestor is arrested by riot policemen during clashes Photograph: Orestis Panagiotou/guardian.co.uk

Demonstrators burn a Greek flag during clashes in central Athens Photograph: Angelos Tzortzinis/guardian.co.uk

Demonstrators clash with riot police during a protest in Athens Photograph: Aris Messinis/guardian.co.uk

Police try to destroy a banner while attacking demonstrators in central Athens Photograph: Louisa Gouliamaki/guardian.co.uk

Police detain an injured demonstrator during a massive demonstration Photograph: Louisa Gouliamaki/guardian.co.uk

A black and red flag is placed where a Greek flag usually flies atop the Athens Academy Photograph: Louisa Gouliamaki/guardian.co.uk

Police carries a detained demonstrator in central Athens, during a massive demonstration commemorating 15-year-old Alexandros Grigoropoulos' fatal shooting a year ago. Police clashed with hooded youths as violence flared in demonstrations marking the anniversary of a teenager's killing by a policeman last year Photograph: Louisa Gouliamaki/guardian.co.uk

Protesters throw stones at policemen during a march in Athens Photograph: John Kolesidis/guardian.co.uk

Protesters are detained by policemen during a march Photograph: Orestis Panagiotou/guardian.co.uk

Youths clash with police in central Athens Photograph: Aris Messinis/guardian.co.uk

A T shirt with a portrait of 15-year-old Alexis Grigoropoulos, who was killed by a policeman's bullet last year, at the site of his death in Exarchia, Athens Photograph: Angelos Tzortzinis/guardian.co.uk

Greek riot police stand around of a statue of a 20th century Greek statesman Eleftherios Venizelos outside the Greek Parliament during clashes in central Athens Photograph: Aris Messinis/guardian.co.uk

Greek youths clash with riot police during a demonstration Photograph: Milos Bicanski/guardian.co.uk

Police detains a demonstrator during a massive demonstration Photograph: Louisa Gouliamaki/guardian.co.uk

Protesters hurl stones at riot policemen during clashes Photograph: Simela Pantzartzi/guardian.co.uk

Devcember 7 20098: Protestors use cream to protect themselves from tear gas Photograph: Orestis Panagiotou/guardian.co.uk

December 7 2009: Police stand around a detained youth Photograph: Aris Messinis/guardian.co.uk

Protesters clash with riot police during a demonstration a day after the first anniversary of the killing of a teenager by police in Athens Photograph: Simela Pantzartzi/guardian.co.uk

December 7, 2009: A protester prepares to throw a petrol bomb at riot police Photograph: Yiorgos Karahalis/guardian.co.uk

December 7 2009: Riot police members protect themselves from missiles Photograph: Aris Messinis/guardian.co.uk

December 7, 2009: Riot police detain a youth during clashes Photograph: Aris Messinis/guardian.co.uk