The Puma helicopters came down in the early hours of Sunday in a rural area near Taji, site of a large US base. US forces had secured the crash site, Mr Browne said.

Two of the four injured had already been discharged and had returned to their units. The other two injured remain in a US military hospital - one remains in a "very serious" condition.

Mr Browne said: "Back here in the UK our focus is of course in supporting the families of those killed or injured in this incident. Our thoughts are with them at this very difficult time."

The BBC understands the helicopters had been taking part in a special forces mission.

Puma helicopters - mainly used to transport troops and equipment - are normally flown by the RAF.

However a Ministry of Defence spokesman would not confirm which regiment the dead personnel belonged to.

Earlier reports had incorrectly identified the crashed helicopters as American.

Prime Minister Tony Blair said it was a "terrible time" for the families of the two UK service personnel who had died, but insisted British foreign policy was "justified and right".

Retired Wing Commander Andrew Brooks told BBC News 24 that Pumas had been in service for around 30 years and were getting elderly.

The military had to use them in Iraq, he said, because the roads were not safe.

Further fighting

The two deaths bring the total number of British fatalities since the 2003 invasion of Iraq to 142.

Meanwhile, British troops have been involved in more fighting with a Shia militia group in the southern Iraqi city of Basra.

Five gunmen from the Mehdi army militia are thought to have been killed in an exchange of fire.

It follows an incident on Friday night when British forces killed eight members of the militia as they were apparently laying mines.

The incident was in the same area where a British Warrior armoured vehicle was hit by a roadside bomb eleven days ago, killing four troops and their Iraqi interpreter.