Three Marines and a sailor were killed during combat in restive Diyala province, where operations are under way to clear the city of Sunni insurgents, Shi'ite militiamen and al-Qaida in Iraq fighters, the US military reported Thursday. The four perished on Tuesday, according to a military release. Earlier Thursday, the military said a soldier was killed in a gunbattle Wednesday in southern Baghdad. A Marine also died Sunday in a non-combat related incident in Anbar province, west of Baghdad, the military said separately. Identities of the dead were withheld pending notification of relatives.