Youths smashed windows and threw rocks at police in central Athens Friday, the seventh day of clashes that erupted after a police officer killed a 15-year-old boy last Saturday.Protesters, described as mostly students, were seen smashing the glass doors of a Citibank, throwing a metal barricade at police lined up along a street and scuffling with police wearing white helmets. Many of the officers were wearing riot gear. One image showed a something that looked like blood on a curb. Tourists were advised to stay in their hotels while thousands of demonstrators shouted and police outside. Journalist Anthee Carassava said the protests were expected to continue into the evening. The official ballistics report from last weekend's shooting was expected to be released Friday. The teen who was shot and other youths had been throwing stones at a police patrol car.The riots that followed soon became an outlet for simmering anger about the economy, education and jobs. The unrest is threatening the government's hold on power, with some opposition groups calling for fresh elections. The two officers involved in Saturday's shooting were remanded into custody Wednesday pending trial. One is charged with premeditated manslaughter and the other with acting as an accomplice.