A soldier was on patrol in Sangin, Helmand province
A British soldier has been killed in an explosion while on a routine foot patrol in southern Afghanistan, the Ministry of Defence has said.
The soldier was from 1st Battalion, the Royal Irish Regiment.
Lt Col David Reynolds, spokesman for British Forces in Afghanistan, said: "This is a tragic loss."
Next of kin have been informed. The death brings the number of soldiers killed on operations in Afghanistan since 2001 to 117.
The Ministry of Defence said the explosion, near Sangin district centre early on Thursday, was believed to have been from an improvised explosive device.
The soldier was given first aid but died later.
Lt Col Reynolds said: "Our thoughts and sympathies are with the friends and family at this most difficult time."
Brig Gen Richard Blanchette, International Security Assistance Force spokesman, offered his condolences to relatives.
He said: "This soldier died honourably, helping bring security to Afghanistan."
Northern Ireland politicians extended their sympathies to the soldier's family and friends.
'Debt of gratitude'
First Minister Peter Robinson said he was shocked and saddened by the death.
"We owe a great debt of gratitude to him and the young people who are fighting to build peace and stability in Afghanistan and protect us from the threat of international terrorism.
"The people of Northern Ireland will be deeply saddened to hear of his death and I would like to take this opportunity to extend my sympathy to his family and his colleagues who continue to fight in Afghanistan."
Northern Ireland Secretary Shaun Woodward said his thoughts were with the soldier's family and his regiment.
The soldier is expected to be named by the MoD on Friday.