Two women, one pregnant, were killed by US troops on Wednesday as they rushed to the hospital in the central Iraqi city of Samarra after their car mistakenly took a road restricted to military traffic, local police said.

Though such incidents occur fairly regularly, they have come under new scrutiny in the wake of investigations into an alleged marine rampage in the western town of Haditha in November that left 24 civilians dead.

A preliminary military inquiry found evidence that US Marines killed two dozen Iraqi civilians in an unprovoked attack in November, contradicting the troops' account, US officials said on Wednesday.

President George W. Bush said he was troubled by news stories on the November 19 killings of men, women and children in the town of Haditha, and a general at the Pentagon said the incident could complicate the job for the 130,000 US troops in Iraq.

"Allegations such as this, regardless of how they are borne out by the facts, can have an effect on the ability of US forces to continue to operate," Army Brig. Gen. Carter Ham, deputy director for regional operations for the military's Joint Staff, told a Pentagon briefing.