Two British servicemen have been shot dead by Afghan police in Helmand province in a suspected 'green on blue' attack, the Ministry of Defence said today.

The soldiers, one from the 1st Battalion Welsh guards and the other a Royal Air Force airman, were killed in the Lashkar Gah district yesterday.

Next of kin have been informed.

A spokesman from the International Security Assistance Force (ISAF) today claimed the attack was carried out by two individuals wearing Afghan national police force uniforms.

One of the attackers is thought to be still at large, and the other was killed when allied forces returned fire.

The two deceased soldiers were members of an advisory team providing security for a meeting with Afghan officials near Patrol Base Attal.

The incident would appear to be another in a series of so-called 'green on blue' attacks where Afghan security forces have attacked international allies.

Sergeant Luke Taylor, of the Royal Marines, and Lance Corporal Michael Foley, of the Adjutant General's Corps (Staff and Personnel Support) were shot dead by an Afghan soldier at the UK headquarters in Helmand in March.

Five British soldiers were killed by an Afghan policeman in November 2009.

The gunman opened fire on the men in a military compound in Nad e-Ali before fleeing. The Taliban later claimed responsibility.

The victims were Warrant Officer Class 1 Darren Chant, 40, from Walthamstow, London, Sergeant Matthew Telford, 37, from Grimsby, and Guardsman Jimmy Major, 18, also from Grimsby, all members of 1st Battalion The Grenadier Guards.

Royal Military Policemen Corporal Steven Boote, 22, from Birkenhead, and Corporal Nicholas Webster-Smith, 24, from Brackley, Northamptonshire, were also killed.

Since the burning of copies of the Koran at a US base in February such attacks have become increasingly common.

Responding to the deaths, Defence Secretary Philip Hammond said,

“What appears to have happened is that an Afghan police officer opened fire on a mentoring team working with the Afghan police. One of the assailants was killed, we think, by other Afghan police officers, one escaped,” he told BBC1's The Andrew Marr Show.

He added: “British forces work alongside Afghan forces everyday with thousands of contacts with them everyday. This is a country that has an insurgency going on in it and, sadly, occasionally, these events occur.

“We don't yet know what the motive was, we don't yet know whether this was an insurgent who'd infiltrated the police or whether it was a policeman who simply had a grievance of some kind.