The soldiers, who died on Tuesday, were in a Mastiff armored vehicle. They were evacuated by air to the military hospital at Camp Bastion but they could not be saved.

Another six soldiers were injured in Tuesday's blast, which occurred during a routine patrol in the district of Nahr-e Saraj.

The number of UK soldiers killed since the laumch of US-led war in Afghanistan in 2001 stands at 444.

The latest deaths bring the total of British troops killed in Afghanistan this year to six.

British troops are due to leave Afghanistan by the end of 2014, when all NATO combat operations are due to finish, although a small number will remain in support roles.

The number of British troops in Afghanistan was reduced to 9,000 before the end of 2012 and is set to fall to 5,200 by the end of 2013.