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.