More than 6,000 police will be on the streets of Athens as the city on Sunday marks the first anniversary of the fatal shooting of a 15-year-old boy. The teenager's death at the hands of police in December last year sparked Greece's worst riots in decades. In the run-up to the anniversary, dozens of schools and university campuses have been occupied by students preparing to mark the uprising. Family and friends of teenager Alexandros Grigoropoulos will hold a memorial service to mark a year since his killing. The government says it will have a zero tolerance policy towards violence. Police said they expect about 150 foreign anarchists to arrive from Italy, France and other European countries. Prime Minister George Papandreou has acknowledged that the weekend is a crucial moment for his new socialist government and for the nation.<br/>