A soldier from 1st Battalion Grenadier Guards was killed in Afghanistan after his vehicle hit a roadside bomb, the Ministry of Defence has said.
The death was unrelated to the attack at Camp Bastion in which two US Marines were killed, the MoD stressed.
The Guardsman died when his vehicle hit an improvised explosive device in the Nahr-e Saraj district of Helmand Province. Next of kin have been told.
Spokesman for Task Force Helmand, Major Laurence Roche, said: "I am very sorry to announce that a soldier from 1st Battalion Grenadier Guards died yesterday when the vehicle he was travelling in struck an improvised explosive device. The thoughts of every one of us serving in Afghanistan are with his family, friends and fellow guardsmen at this time."
The death brings to 428 the number of members of UK forces to have died since operations in Afghanistan began in October 2001.
Earlier this week tributes were paid to "superb" soldier Sergeant Lee Paul Davidson, 32, from Doncaster, who was killed in another IED attack on Sunday.
The father of two, whose wife is pregnant with his daughter, was also in Nahr-e Saraj when his Ridgeback vehicle was attacked.
In an unrelated incident, Nato said a man believed to be a member of the Afghan Local Police had turned his weapon on US-led coalition forces, killing two international service members.
The rising number of insider attacks is complicating plans to train Afghan forces so that most foreign troops can withdraw from the country by the end of 2014.
In a statement, Nato said that the gunman in the shooting in southern Afghanistan was killed during the attack.