Greek police have been attacked with firebombs and stones on a seventh day of riots following the killing of a student by police. Riot police fired tear gas at the protesters who carried banners saying "The state kills" and "The government is guilty of murder", to try to stop dozens breaking their lines. The police have struggled to dampen the anger of young Greeks over the killing of 15-year-old Alexandros Grigoropoulos, rising unemployment and low wages. Hundreds of cars, banks and businesses have been wrecked in rioting, prompted by the shooting on December 6. Police sources said they have begun to run out of teargas after using more than 4,600 capsules in the last week and have urgently contacted Israel and Germany to replenish supplies. Maria Tsoupri, 22, said: "Everyone thinks this government that murders has to fall. The government in four years has only carried out reforms against students. We don't see a future. We have a future only through struggle." Prime Minister Costas Karamanlis, whose popularity ratings have dived in recent months, expressed sorrow at the shooting but has condemned the destruction of private property. On Thursday, dozens of protesters hurled fire bombs and stones at riot police in central Athens but the damage was small compared to previous nights and heavy rain helped extinguish the demonstrations early. Greeks have also protested in London, Paris, Berlin, Rome, The Hague, Moscow, New York, Italy and Cyprus.