Police fired teargas at rioters who threw rocks and firecrackers in central Athens as thousands gathered to mark the first anniversary of the police shooting of a teenager. Clashes broke out as about 3,000 people, mostly students, anarchists and leftists, began a march to parliament. More protests were expected tomorrow. An evening memorial service was planned in the Exarchia district, where 15-year-old Alexandros Grigoropoulos was shot dead.