Coalition forces are to scale back operations with Afghan soldiers and policemen following a string of so-called "green on blue" attacks in which local recruits turn their weapons on international allies. Most joint patrols and advisory work with Afghan troops will now only be conducted at the battalion level and above, while co-operation with smaller units will have to be "evaluated on a case-by-case basis and approved by RC (regional) commanders", the International Security Assistance Force (ISAF) said in a statement.

The move comes amid mounting concern over "green on blue" attacks on coalition forces. So far this year, 51 international troops have been killed by Afghan forces or militants wearing their uniforms. The Ministry of Defence said there had been 18 "green on blue" UK fatalities since 2008, including the nine killed this year. In 2011, there was only one such death.

At the weekend two soldiers from Yorkshire soldiers were killed by an attacker dressed as an Afghan policeman and feigning injury. Married father-of-two Sergeant Gareth Thursby, was 29 and from Skipton. Private Thomas Wroe, aged 18, was from Meltham. Both from the 3rd Battalion The Yorkshire Regiment (Duke of Wellington's), they were shot dead at a checkpoint on Saturday in the south of Nahr-e Saraj district, Helmand province.

ISAF insisted in its statement that it remained committed to its partnership with the Afghan National Security Forces. (ANSF)

Most partnering and advising will now be at the Kandak (Battalion) level and above. This does not mean there will be no partnering below that level - the need for that will be evaluated on a case-by-case basis and approved by RC (regional) commanders. In some cases, ANSF are fully capable of increased independent activity and their advisers will simply be stepping back to advise from the next level. Make no mistake about it: we remain committed to our partnership with the ANSF, and we continue to move forward and will meet our campaign objectives."

The ISAF announcement was made as it was revealed that an Afghan and coalition security force has arrested one of the Taliban leaders thought to have been behind the attack on Friday at Camp Bastion, in Helmand province, where the bulk of UK's 9,500-strong force in Afghanistan are deployed.

ISAF said the man was taken into custody by the security force in the Nad 'Ali district by the force following joint efforts by Afghan and coalition forces to track down insurgents responsible for the assault. The Taliban leader is suspected of having provided support for the attack in which two US Marines were killed and six planes destroyed. Taliban sources claimed Bastion was targeted because Prince Harry is serving there as an Apache attack helicopter gunner.