Police say six people were detained during Sunday's demonstration in central Athens. About 600 people attended the rally, which featured heated speeches but was mostly peaceful.
It briefly turned violent when some in the crowd clashed with riot police, throwing objects at them. Three cars were damaged and three storefronts smashed.
Police had cordoned off Omonia Square and prevented the protesters from marching to the U.S. Embassy, about three kilometers (two miles) away.
Banners in English denounced the film, called on the U.S. to hang the filmmaker and told President Barack Obama "we are all with Osama."
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