ATHENS, December 21 (RIA Novosti) - Hundreds of Greek youths staged fresh protests in Athens, clashing with police amid Greece's worst riots in decades sparked by the recent killing of a teenager by police, local TV channels reported Sunday.

Students threw stones and firebombs at police in the Athens district of Exarchia where 15-year-old Alexandros Grigoropoulos had been shot dead on December 6, and also erected roadblocks around the nearby Polytechnic University. The police responded with tear gas, TV channels said.

The riots, sparked by the youth's killing, earlier spread to other Greek cities, leaving a trail of destruction as youths went on the rampage looting shops and setting fire to hundreds of cars, banks and businesses.

A recent opinion poll published by the Ethnos newspaper said 83% of Greeks were unhappy with the methods used by the government to deal with the violence.

Two police officers have been detained over the teenager's killing. One of them, Epaminondas Korkoneas, who claims he fired warning shots in self-defense which ricocheted, was charged with murder and the illegal use of his weapon. The second officer, Vassilios Saraliotis, was charged with aiding and betting Korkoneas