Hooded youths smashed bus shelters and threw rocks and Molotov cocktails soon after a march began in the Greek capital. Police responded with tear gas and arrested 10 people.
There were similar incidents in the northern city of Thessaloniki.
The teenager's killing on December 6, 2008, sparked major riots that spread from Athens across the country, lasting for weeks. The 15-year-old died after he was shot by a policeman. Grigoropoulos had been on a night out with friends in Athens' Exarcheia district at the time.
Fueled by economic frustrationThe policeman, who claimed he had fired into the air when youths attacked him, was sentenced to life in prison. A second policeman present at the shooting was sentenced to 10 years, but was granted a conditional release several years ago.
Read more: Greeks recall 1973 student defiance of junta
A second march was scheduled for later in the day in Athens, with a gathering to be held on Thursday night at the place where Grigoropoulos died.
Since 2009, annual marches marking the anniversary have often turned violent. Although the unrest was originally triggered by Grigoropoulos' death, its continuation has been linked with frustration among young people over austerity and high youth unemployment in Greece since then.
rc/amp (dpa, AP)
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