Students occupying an Athens university clashed with police on Thursday and vowed more protests in coming days.
Youths threw stones and fire bombs at police before dawn in a sixth day of protests since the shooting of Alexandros Grigoropoulos, aged 15, ignited anger at police brutality and rising economic hardships due to the global economic slowdown.
Early morning violence gave way to calm as Greeks returned to work after a 24-hour general strike on Wednesday called by unions against the government's economic policies.
But many people asked what would happen next after the worst riots in Greece since military rule ended in 1974.
School and university students and teachers have called a rally in Athens for Friday at the teenager's shooting, and further demonstrations are planned for next week.
Many people were angry that the policeman charged with murdering the teenager did not express remorse to investigators on Wednesday. He said he fired warning shots in self-defence which ricocheted to kill the youth.
Epaminondas Korkoneas and his partner, who is charged as an accomplice, were sent to jail pending trial by a prosecutor on Wednesday. Cases in Greece often take months to reach court.
Business as usual - govt
Prime Minister Costas Karamanlis, who has announced financial support for hundreds of businesses damaged in the rioting, was due to travel to Brussels for an European Union summit on Thursday, as the government tried to carry on business as usual.
Mr Karamanlis and opposition leader George Papandreou appealed for an end to the violence, which hit at least 10 Greek cities and damaged hundreds of millions of euros in property.
Greeks also protested in Paris, Berlin, London, Rome, The Hague, Moscow, New York, Italy and Cyprus.
While the government, which has a one-seat majority in parliament, appeared to have weathered the immediate storm, analysts said its hands-off response to the rioting has damaged its popularity ratings which are already low.
The opposition socialist party, which leads in the polls, has called for an election.