A British soldier was killed in Iraq today after a Puma helicopter crashed at Basra airport.
Defence Secretary Geoff Hoon said it appeared "unlikely" that the aircraft was brought down by hostile action.
Two other RAF crew members were injured during the incident this morning at the airfield in southern Iraq.
Speaking during defence questions in the House of Commons, Mr Hoon told MPs: "It appears unlikely that hostile action was the case but it is too soon to confirm any other details."
Captain Hasham Hallawi, spokesman for UK forces in Basra, also said foul play was not suspected.
The fatality brings to 61 the number of British personnel killed since the start of the Iraqi conflict.
MoD staff in Iraq's second city said it could be weeks before the circumstances are established.
The helicopter was part of 33 Squadron from RAF Benson, Oxfordshire.
It is not known if the helicopter, commonly used for carrying troops, came down while attempting to take off or while at low altitude.
"What we know is that the helicopter crashed this morning local time, but there will have to be an investigation to determine why," said a spokesman.
"No other helicopters have been grounded as a result and the accident has not affected the way we are carrying out missions."
The two injured crew members were given check-ups at a local hospital but were not seriously hurt.
The identity of the deceased has not yet been released.
A statement on the MoD website said: "A British serviceman was tragically killed in an accident at Basra International Airport to an RAF Puma helicopter.
"The next of kin are being informed and further details will not be published until this process is complete."
The Puma is a twin-engined support helicopter capable of carrying up to 20 troops. It entered service with the RAF in 1971.
Pumas are used for tactical movement of troops, weapons, ammunition and support stores, as well as casualty evacuation.
The last British soldier to die in Iraq was Fusilier Gordon Gentle on June 28.
The 19-year-old from the 1st Battalion Royal Highland Fusiliers was killed in an improvised explosive device attack on British military vehicles in Basra.