Two British soldiers have been killed in southern Afghanistan, the Ministry of Defence said today.
Another six members of Nato forces were wounded in the attack in Helmand Province yesterday involving an improvised explosive device (IED).
News of the British fatalities came as American forces launched a massive pre-dawn operation in Taliban-controlled areas of Helmand.
One of the dead soldiers was serving with the 1st Battalion Welsh Guards, the other was a member of the 2nd Royal Tank Regiment.
A Ministry of Defence spokesman said the soldiers were killed while on Operation Panthers Claw near Lashkar Gah in central Helmand province.
Spokesman for Task Force Helmand, Lieutenant Colonel Nick Richardson, said: "The loss of these brave soldiers has hit us all very deeply; we grieve for them at this very sad time.
"Our thoughts and prayers are with their families, friends and colleagues who feel the greatest loss."
The MoD said the soldiers' next of kin had been informed and had asked for a 24 hour period of grace before further details were released.
Commenting on the casualties, Brigadier-General Eric Tremblay, spokesman for Nato's International Security Assistance Force (Isaf) in Afghanistan, said: "I wish to convey our most sincere sympathies to the family members and friends of these brave soldiers.
"Our thoughts and prayers are with them in this most difficult time.
"Isaf's efforts are dangerous and difficult but we are committed to helping build a safe and prosperous Afghanistan and we will succeed in this endeavour."
The deaths took the number of UK servicemen and women who have died in Afghanistan since the start of operations in October 2001 to 171.
Today's US operation in Helmand involved nearly 4,000 newly-arrived US Marines and 650 Afghan troops.
The operation - named Khanjar, or Strike of the Sword - is aimed at clearing insurgents from the region ahead of Afghanistan's presidential election in August.
It follows the British assault, Operation Panthers Claw, launched to drive the Taliban out of strongholds in and around Babaji, north of Lashkar Gah in Helmand.
Some 350 troops from the Black Watch, 3rd Battalion The Royal Regiment of Scotland, launched the attack on June 19 in one of the UK military's biggest co-ordinated air operations of modern times.
The bulk of the 9,000 British servicemen and women in Afghanistan - including around 700 personnel sent out to provide extra security in the run-up to the election - are stationed in Helmand.
Limited numbers of American forces have been operating in Helmand for some time, including around the town of Now Zad.
But in recent months they have been bolstered by around 10,000 extra troops as part of US President Barack Obama's military surge in Afghanistan.
Senior British officers acknowledge UK forces are stretched in Helmand but say they are not being "bailed out" by the Americans.
They point out that the new US troops have moved into remoter parts of Helmand, while the British retain responsibility for the more densely-populated central and eastern areas.Reuse content