Riot police in Belgrade were unable to stop angry demonstrators from setting fire to the U.S. embassy, with flames damaging at least one office inside the building.
The incident took place after a smaller group of protesters broke off from a larger demonstration against the recent declaration of independence by the ethnic Albanian majority government in Kosovo, a former province of Serbia.
The attackers, many of them wearing masks, used fire bombs and rocks to attack the building, which was closed earlier this week.
Eyewitnesses said at least one protester climbed up to the first floor of the building, ripping the American flag off its pole and briefly putting a Serbian flag in its place. The protesters then burned the American flag before Serb police chased the demonstrators away from the building.
The attack came after a massive demonstration in Belgrade protesting Kosovo's recent declaration of independence, and the decision by the United States and several European countries to recognize the independence move.
A number of the protesters carried signs that read "Stop USA terror."