Serb rioters broke into the U.S. Embassy Thursday and set fire to an office after a massive protest against Kosovo's independence that drew an estimated 150,000 people.
Masked attackers broke into the building, which has been closed this week, and tried to throw furniture from an office. A blaze broke out inside one of the offices and parts of the facade also caught fire.
Authorities drove armored jeeps down the street and fired tear gas to clear the crowd. The protesters dispersed into side streets where they continued clashing with authorities.
The neighboring Croatian Embassy also was attacked by the same group of protesters.
In Washington, State Department spokesman Sean McCormack strongly urged the Serbian government to protect the U.S. Embassy. He said the U.S. ambassador was at his home and was in contact with U.S. officials.
More than a dozen nations have recognized Kosovo's declaration of independence on Sunday, including the United States, Britain, France and Germany.
But the declaration by Kosovo's ethnic Albanian leadership has been rejected by Serbia's government and the ethnic Serbians who populate northern Kosovo. Russia, China and numerous other nations have also condemned the declaration, saying it sets a precedent that separatist groups around the world will seek to emulate.
Kosovo, which is 90 percent ethnic Albanian, has not been under Belgrade's control since 1999, when NATO launched airstrikes to halt a Serbian crackdown on ethnic Albanian separatists. A U.N. mission has governed Kosovo since, with more than 16,000 NATO troops and KFOR, a multiethnic force, policing the province.
But Serbia -- and Kosovo's Serbs, who make up less than 10 percent of Kosovo's population -- refuse to give up Kosovo, a territory considered the ancient cradle of Serbs' state and religion.
Earlier Thursday, police estimated that about 150,000 people had attended a rally in the Serbian capital. The crowd waved Serbian flags and carried signs reading "Stop USA terror." One group set fire to a red-and-black Albanian flag.