"Three marines assigned to 1st Marine Expeditionary Force were killed in action September 24 in two unrelated incidents, while conducting security and stability operations in the Al-Anbar province," a statement said without elaborating.

Another statement announced the death of a fourth marine in a third incident, also on Friday.

Al-Anbar province includes the Sunni Arab insurgent bastions of Fallujah and Ramadi, as well as the troubled Syrian border district.

Based on Pentagon figures, the latest deaths bring to 1,043 the number of US troops killed in Iraq since last year's invasion.