NATO says three U.S. service members have been killed in two bombings in southern Afghanistan.

Statements from the international military coalition say the Americans died Sunday in separate strikes but gives no further details. It's the second day of deadly attacks on U.S. troops in the south, which is expected to be the main focus of a U.S. troop surge.

At least 25 American deaths have been reported so far this month — compared with 14 for the whole of January last year.