Four other US Marines were reported to be seriously wounded in the blast
British officials say a roadside bomb in southern Afghanistan has killed a veteran British war correspondent and a U.S. Marine.
Britain's Defense Ministry says Rupert Hamer, the defense correspondent for the Sunday Mirror newspaper, was killed while accompanying Marines on patrol in Helmand province Saturday.
Photographer Philip Coburn was seriously wounded by the makeshift bomb, as were four other Marines.
Officials retracted earlier reports that an Afghan soldier was among those killed.
Hamer is believed to be the first British journalist to be killed in the Afghan conflict. Prime Minister Gordon Brown has released a statement expressing sympathy for his family, friends and colleagues.
Hamer is the second journalist killed in Afghanistan in as many weeks. Canadian journalist Michelle Lang was killed December 30, also by a roadside bomb.
Meanwhile, U.S. and Afghan authorities have signed a deal that is expected to transfer responsibility for the U.S.-run detention facility at Bagram Air Base by the end of the year.
Afghanistan's Defense Ministry announced Saturday that Afghan troops will soon begin training to take over the investigation, detention and trials of inmates.
The site, near Kabul, has been used to hold detainees since the U.S.-led offensive in Afghanistan began in 2001.
U.S. troops were accused of beating two prisoners to death at Bagram in 2002. Human rights groups have criticized the United States for detaining inmates for lengthy periods of time without charge.
About 700 detainees are being held at Bagram.
Some information for this report was provided by AP, Reuters .