Two UK military personnel have been killed and two seriously injured in an RAF Puma helicopter crash near Baghdad in Iraq, defence officials have said.
An RAF Board of Inquiry is heading to Iraq to investigate Tuesday's crash, but the Ministry of Defence said it was too early to speculate on the cause.
The two injured personnel are recovering in hospital and the next of kin of those killed have been informed.
The crash is not believed to be the result of enemy fire.
It is not yet known to which service the military personnel belonged.
The US military issued a statement on Tuesday saying two people had been killed and 12 injured when a coalition helicopter crashed near Salman Pak, on the outskirts of the Iraqi capital.
But a spokesman for the UK defence ministry said he could not confirm whether this was the same incident but the details did appear to match.
Defence chiefs said their thoughts were "with the families" of all involved.
The deaths on Tuesday take the total number of UK troops killed in operations in Iraq since the 2003 invasion to 173.