Greece has seen another day of violent clashes that erupted over last year's police shooting of the 15-year-old teenager Alexis Grigoropoulos.
Greek police were out in force again on Monday
Greek riot police clashed with hundreds of stone-throwing youths in Athens on Monday as protesters took to the streets for a second day.
Security forces made 21 arrests after scores of stone-throwing youths separated from the throng of 5,000 demonstrators marching towards parliament.
Two youths were arrested earlier on Monday for throwing stones at a police station in Athens. Two other police stations in the suburbs of Agia Paraskevi and Kallithea were also attacked, police said.
Police fired tear gas to disperse protesters
In the northern city of Thessaloniki police fired teargas at dozens of violent youths, who broke away from a march of 2,500 people.
"The clashes are not significant overall, the protests went as expected," said a police official who declined to be named.
University rector in intensive care
Police also formed a cordon around the University of Athens to keep protesters off the premises.
The rector of the university, Christos Kittas, had been injured on Sunday when dozens of hooded youths stormed the building in the city center.
Kittas remained in intensive care on Monday after being hospitalized for head injuries and an irregular heartbeat.
Greek authorities had deployed some 6,000 police officers in the capital to prevent a repeat of the violent weekend demonstrations which saw at least 30 people injured and dozens arrested around the country.
"The message sent is that Athens and Greece's major cities are not defenseless," said government spokesman George Petalotis.
Police have been accused of using excessive force
The police department said 26 officers and four protesters were hurt in Sunday's clashes. Some protesters who did not take part in the clashes accused police of excessive force.
Police reportedly made 125 arrests during the weekend protests in Athens, Thessaloniki, Patras, Rhodes and Heraklion.
Teenager Alexis Grigoropoulos was shot dead on December 6, 2008, by a police officer who claimed to have fired into the air whilst under attack from youths. The incident last year triggered the worst rioting in Greece in decades.
Editor: Susan Houlton