A roadside bomb blast in western Iraq has killed 14 U.S. Marines and their civilian interpreter, in the deadliest attack on U.S. forces since last December. U.S. authorities say the bomb exploded under an armored Marine vehicle about 200 kilometers northwest of Baghdad. Wednesday's bombing outside (the town of) Haditha occurred in the same area where six Marines were killed in an insurgent ambush late Monday. Al-Qaida-linked insurgents claimed responsibility for Monday's attack and claimed one wounded Marine was captured near Haditha. The claim has not been verified, and U.S. commanders say all U.S. forces in the region were accounted for. Late today, the insurgent group Army of Ansar al-Sunna posted a video showing a bullet-riddled body it said was a Marine killed in an unspecified attack. There has been no U.S. reaction to the posting. The Pentagon says the U.S. deaths came as part of an ongoing U.S. offensive in the area.