Students shouting "Drive out Yankees!" attacked a U.S. government office, firebombed a police bus and injured 13 officers Friday, police and U.S. officials said.

Two police were seriously hurt in the battle in the southern city of Kwangju, the U.S. Embassy said in a statement. Police said four protesters were arrested.About 100 protesters, many with iron pipes and clubs, hurled rocks and about 150 gasoline bombs at the U.S. Information Service building, the statement said.