A military statement on Friday said four marines died when a bomb went off in Gharma, near Falluja, on Thursday.

Falluja, about 50 west of Baghdad, is a stronghold of Sunni Arab opposition to US occupation and the Shia-led government.

Two more marines were killed on Thursday by a roadside bomb while on patrol in the vicinity of Qaim near the Syrian border, where the US forces are conducting a major combat operation aimed at flushing out anti-government fighters, a separate military statement said.

US and British in Iraq have been repeatedly attacked in recent months by "shaped charges" which are able to pierce armour and hence much more deadly than conventional roadside bombs.