The Royal Air Force C-130 Hercules went down northwest of Baghdad at 4.40pm (1340 GMT) on Sunday, according to the military press office in Baghdad.
Military sources told Britain's domestic Press Association news agency the number killed in the crash was around 10, with it unlikely to be more than 15.
The cause of the crash was not immediately clear.
In a televised speech on Sunday, British Prime Minister Tony Blair said "people lost their lives" in the crash, but not specifying how many had perished or providing any other details.
"This country and the wider world will never forget them," Blair said.
The C-130 Hercules transport plane involved in the crash can carry up to 92 soldeirs, 64 paratroopers or military equipment.
No information has been released about the cause of the
crash, but US officials said helicopters had spotted the
wreckage, which was strewn over a wide area.
Bound for Balad
The British Ministry of Defence, announcing the crash earlier
in the day, said: "An RAF C-130 Hercules crashed at around 1725 local time (1425 GMT) on 30 January some 30km northwest of Baghdad."
Media reports said the aircraft was on its way to the city
of Balad from Baghdad when it crashed.
Balad houses one of the largest US airbases in Iraq and has two runways, according to Britain's Press Association. Its 25-square-kilometre airfield is protected by a 20km security perimeter.
British and US troops were helping Iraqi forces provide
security on Sunday as Iraqis voted in the first national
election since the US-led invasion in March 2003.
On Wednesday, 30 US marines and one sailor were killed
when an American military helicopter crashed close to the
Jordanian border in the deadliest single incident for American
troops since they invaded Iraq.