Tony Blair yesterday insisted the UK's foreign policy was "justified and right" as he expressed his sympathy for the families of an airman and a soldier killed when two helicopters crashed in Iraq.

Initial reports suggested the crash, which happened north of Baghdad yesterday morning and involved two British Puma helicopters, was an accident and not caused by an insurgent attack.

The Prime Minister said: "It's true that in Iraq, Afghanistan, Kosovo, Sierra Leone, we've had a hugely interventionist foreign policy: a different type of foreign policy from the one that has gone before, that's true.

"But I believe it's justified and right. I reflect again as we've lost forces in Iraq today for the families this is always a terrible time, a time of great grief and anguish.

"But what our forces are doing there, what British forces are doing in Iraq and Afghanistan, is they are fighting the same forces of terrorism and extremism that are operating around the world today.

"I believe in time people will realise why it is important that we fight these people wherever they are."

The Ministry of Defence confirmed last night there were a total of six casualties in the crash, all from the same helicopter.

Two people were killed, one from the RAF and the other from the Army, and four others were injured.

Two of the injured have already been discharged back to their units and the other two are being treated in a US hospital.

It is not known exactly how many people were on board the two helicopters, which are normally flown by the RAF and can carry up to 16 fully-equipped troops.

British forces are based in southern Iraq but UK units - including special forces troops - carry out missions all over the country.

An MoD spokesman said: "I can't talk about the particular mission they were involved in but we do have units operating as part of the coalition across Iraq."

It is believed some, but not all, of those on board the crashed Pumas were special forces. British and US special forces operate out of the US air base and supply hub at Balad, 60 miles north of Baghdad in the heart of the Sunni Triangle.

The city is home to 100,000 Shia Iraqi civilians and is the single biggest grouping of the sect in the Sunni-dominated north of the country.

Des Browne, Defence Secretary, said: "I have been deeply saddened by the loss of two of our brave service personnel in northern Iraq.

"Each tragic incident of this type is another reminder of the daily risks that our servicemen and women face in the course of their important duties."

He said Puma helicopters had a "very good safety record", adding: "Although both helicopters have been damaged we intend to recover both of them.

"I am grateful to the US forces who were able to seal off the area quickly."

Officials have already contacted the next of kin of everybody on board the two helicopters at the time of the crash.

Yesterday's deaths bring the total number of British fatalities since hostilities in the country began to 142.

Of those, 109 have died in action, while these latest casualties join the other 31 deaths which have been the result of accidents, non-combat injuries or illness.

Dozens of UK special forces' troopers were transferred from Iraq last year to step up the hunt for al Qaeda leader Osama bin Laden in the mountains along the Afghan-Pakistan border and to carry out reconnaissance missions in support of the British task force in Helmand province. Britain's special forces maintain a presence at Balad and in Baghdad.

Task Force Black, the clandestine unit based in the Iraqi capital, played a central role in rescuing British hostage Norman Kember.