Riot police try to avoid molotov cocktails and stones trown by demonstrators outside parliament in Athens on December 6, 2011 during a demonstration to commemorate the police killing of a student three years ago which sparked violent riots lasting weeks. Pupils and students marched to mark the December 6, 2008 death of Alexis Grigoropoulos, 15, shot by police as Greece first came under pressure from the eurozone debt crisis. AFP PHOTO/ LOUISA GOULIAMAKI

A masked youth throws a petrol bomb at police in Athens' Syntagma (Constitution) square during clashes December 6, 2011. Greek police fired tear gas on Tuesday at dozens of black-clad protesters in Athens who hurled petrol bombs and stones, while hundreds marched to parliament to mark the 2008 shooting of a student by police. REUTERS/Yannis Behrakis

Youths clash with riot police outside the parliament during a demonstration in Athens on December 6, 2011, to commemorate the police killing of a student three years ago which sparked violent riots lasting weeks. Pupils and students marched to mark the December 6, 2008 death of Alexis Grigoropoulos, 15, shot by police as Greece first came under pressure from the eurozone debt crisis. AFP PHOTO/ Angelos Tzortzinis

A protester throws looks towards riot police by the parliament in Athens on December 6, 2011 during a demonstration to commemorate the police killing of a student three years ago which sparked violent riots lasting weeks. Pupils and students marched to mark the December 6, 2008 death of Alexis Grigoropoulos, 15, shot by police as Greece first came under pressure from the eurozone debt crisis. AFP PHOTO/ LOUISA GOULIAMAKI

A protester carries a petrol bomb during a protest at the northern port city of Thessaloniki, Greece, Tuesday, Dec. 6, 2011. Protesting high school students hurled rocks and bottles during a rally to mark the third anniversary of the fatal police shooting of a teenager in central Athens. (AP Photo/Nikolas Giakoumidis)

A youth gathers stones near the parliament in Athens on December 6, 2011 during a demonstration to commemorate the police killing of a student three years ago which sparked violent riots lasting weeks. Pupils and students marched to mark the December 6, 2008 death of Alexis Grigoropoulos, 15, shot by police as Greece first came under pressure from the eurozone debt crisis. AFP PHOTO/ LOUISA GOULIAMAKI

Riot police look on as a molotov cocktail thrown by youths exploeds in front of the parliament in Athens on December 6, 2011 during a demonstration to commemorate the police killing of a student three years ago which sparked violent riots lasting weeks. Pupils and students marched to mark the December 6, 2008 death of Alexis Grigoropoulos, 15, shot by police as Greece first came under pressure from the eurozone debt crisis. AFP PHOTO/ARIS MESSINIS

Riot police chase a youth during clashes outside the parliament on December 6, 2011, as about 1,000 school pupils marched to commemorate the police killing of a student three years ago which sparked violent riots lasting weeks. Pupils and students marched to mark the December 6, 2008 death of Alexis Grigoropoulos, 15, shot by police as Greece first came under pressure from the eurozone debt crisis. AFP PHOTO / ARIS MESSINIS

Youths clash with riot police outside the parliament during a demonstration on December 6, 2011, to commemorate the police killing of a student three years ago which sparked violent riots lasting weeks. Pupils and students marched to mark the December 6, 2008 death of Alexis Grigoropoulos, 15, shot by police as Greece first came under pressure from the eurozone debt crisis. AFP PHOTO / ARIS MESSINIS

Youths clash with riot police outside the parliament during a demonstration on December 6, 2011, to commemorate the police killing of a student three years ago which sparked violent riots lasting weeks. Pupils and students marched to mark the December 6, 2008 death of Alexis Grigoropoulos, 15, shot by police as Greece first came under pressure from the eurozone debt crisis. AFP PHOTO / ARIS MESSINIS

A protester throws a petrol bomb against riot police guarding the parliament in Athens' Syntagma (Constitution) square during clashes December 6, 2011. Greek police fired tear gas on Tuesday at dozens of black-clad protesters in Athens who hurled petrol bombs and stones, while hundreds marched to parliament to mark the 2008 shooting of a student by police. REUTERS/Yannis Behrakis

ATHENS, GREECE - DECEMBER 6: Cars are parked in front of graffiti displayed on a building on December 6, 2011 in Athens, Greece. Graffiti artists throughout the city are expressing the effects of austerity measures that have plagued the community as Greece continues to struggle in debt while lawmakers today are set to pass next year's budget. (Photo by Milos Bicanski/Getty Images)

Riot police walk past burning debris outside the parliament in Athens on December 6, 2011, during demonstrations to commemorate the police killing of a student three years ago which sparked violent riots lasting weeks. Pupils and students marched to mark the December 6, 2008 death of Alexis Grigoropoulos, 15, shot by police as Greece first came under pressure from the eurozone debt crisis. AFP PHOTO/ Angelos Tzortzinis

A protester throws a petrol bomb towards riot police guarding the parliament in Athens' Syntagma (Constitution) square during evening clashes December 6, 2011. Fresh clashes broke out between demonstrators and Greek police outside parliament on Tuesday evening, hours after police fired teargas to disperse youths hurling petrol bombs at them.Protesters, many dressed in black, threw makeshift bombs and stones at police, who responded with teargas and formed a cordon outside parliament. Inside, lawmakers were in the final stages of a debate on the 2012 budget packed with unpopular austerity measures. REUTERS/Yannis Behrakis

A protestor throws a stone at riot police outside the parliament in Athens on December 6, 2011, during demonstrations to commemorate the police killing of a student three years ago which sparked violent riots lasting weeks. Pupils and students marched to mark the December 6, 2008 death of Alexis Grigoropoulos, 15, shot by police as Greece first came under pressure from the eurozone debt crisis. AFP PHOTO/ Angelos Tzortzinis

A protestor throws a molotov cocktail at riot police outside the parliament in Athens on December 6, 2011, during demonstrations to commemorate the police killing of a student three years ago which sparked violent riots lasting weeks. Pupils and students marched to mark the December 6, 2008 death of Alexis Grigoropoulos, 15, shot by police as Greece first came under pressure from the eurozone debt crisis. AFP PHOTO/ Angelos Tzortzinis