Rupert Hamer, 39, was killed covering the conflict when the vehicle he was travelling in hit an improvised explosive device north-west of Nawa. He died at the scene.

His colleague, photographer Philip Coburn, was wounded in the blast, which also left a US Marine dead and four seriously injured, the Ministry of Defence said.

Mr Hamer, who was married with three young children, had worked for the Sunday Mirror for 12 years, taking on the defence correspondent role in 2004. His editor said he was a “fine writer” who was “hugely popular” with his colleagues.

Prime Minister Gordon Brown said: “I was deeply saddened by this tragic news, and my heartfelt thoughts and sympathies are with the families, friends and colleagues of Rupert and Philip.

“Their courage, skill and dedication to reporting from the frontline was incredibly important and ensured that the world could see and read about our heroic troops. Their professionalism and commitment to our forces will not be forgotten.”

Mr Hamer and Mr Coburn, 43, had flown to the region on New Year’s Eve and were embedded with the US Marine Corps when they were caught in the explosion. Mr Coburn is in a serious but stable condition in hospital and is expected to be brought back to Britain today, where he will undergo treatment at Selly Oak Hospital in Birmingham.

Defence Secretary Bob Ainsworth said: “Both Rupert Hamer and Phil Coburn accompanied me on my most recent trip to Afghanistan. I got to know them well and I was impressed by their hard work and professionalism.

“My thoughts and deepest sympathies are with the families, friends and colleagues of both men at this extremely distressing time.

“As a defence correspondent, Rupert Hamer was in regular contact with press officers at the MoD.

“I know they had great respect for his work and the news of his death has been met with great sadness amongst us all.”

He added: “The sacrifice of service personnel is well documented and rightly respected, but this news demonstrates the risks also faced by journalists.”

Tina Weaver, editor of the Sunday Mirror, said Mr Hamer was a “highly-regarded and brave” journalist.

She added that Mr Hamer believed the only place to report a war was from the front line.

She said: “He was a fine, fearless, and skilled writer ... he was a gregarious figure, a wonderful friend who was hugely popular with his colleagues.”