Up to 15 British troops are feared dead after an RAF Hercules aircraft crashed in central Iraq yesterday.
A military sources said the figure was "around ten", with it highly unlikely to be more than 15.
No further details of the casualties were provided last night, the Ministry of Defence said, because next of kin were still being informed.
Prime Minister Tony Blair announced the deaths and paid tribute to those who had been killed.
The aircraft was flying from Baghdad to the city of Balad when it came down 25 miles north of the capital.
Wreckage from the plane was scattered across a wide area. There was no word of possible survivors.
Mr Blair said that the British people were yet again reminded of the sacrifices that the armed forces made on behalf of their country and the extraordinary job they did.
"Our thoughts and prayers are with the families of those who lost their lives earlier today," he said.
The plane, from RAF Lyneham, in Wiltshire, crashed at 4.40pm local time (1.40pm UK time).
A British Army spokesman in Iraq said: "We can confirm that a UK C-130 Hercules has crashed in central Iraq.
"We are not able to confirm the safety of the crew or any passengers. The cause of the crash is not yet known."
Military sources in Iraq said the transport planes rarely travelled north of Baghdad.
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