Police find themselves up against rioters wearing gas masks
Hundreds of anarchist protesters in Greece have fought running battles with police through the centre of the capital, Athens.
The demonstrators were demanding the release of people arrested during rioting last month after a policeman shot dead a youth aged 15.
Rioters smashed shop windows and threw stones and petrol bombs, police say.
Officers responded with baton charges, tear gas and pepper spray and eventually dispersed the crowd.
Compared to the riots that swept Greece last month, Saturday's violence was on a relatively small scale but it showed that anger against the state and the police are still simmering, the BBC's Malcolm Brabant reports from Athens.
The street fighters and anarchists are trying hard to keep alive what they regard as December's insurrection and demonstrations covering a wide range of grievances are taking place on a daily basis, our correspondent says.
But the nature of the clashes may soon change, he adds.
The futility of firing tear gas at rioters who wear gas masks has dawned on the authorities and it is reported that Greece is taking delivery of water cannon, which should be ready for action within a fortnight, our correspondent reports.