Two US civilians were shot dead by an Afghan soldier in northern Afghanistan today as a major international conference agreed a strategy for the withdrawal of foreign troops.
The shooting underlined the difficulty facing Nato forces as they prepare to hand over control over security.
At a major summit in Kabul, ministers from more than 70 nations endorsed a strategy for the withdrawal of Nato-led foreign troops - including about 10,000 from the UK.
The international conference agreed Afghan forces should start taking responsibility for security in areas of their country this year and be in charge of all provinces by the end of 2014.
Coalition forces have been involved in a major push to train up their Afghan counterparts.
But the shooting, involving an Afghan Army trainer at a weapons training area near Mazar-e-Sharif, highlights the difficulties faced by foreign troops.
It also comes after the killing last week of three British servicemen at the hands of an Afghan policeman.
The suspect was also killed in the today's incident, along with another Afghan soldier, during routine weapons proficiency training at the Regional Military Training Centre's Basic Warrior Training Course at Camp Shaheen.
The Afghan soldier appears to have turned on his colleagues and Isaf launched a joint investigation with the Afghan ministry of defence to investigate.
Isaf spokesman Brigadier General Josef Blotz said: "The actions of this individual are not representative of the thousands of men and women who train and fight side-by-side with Isaf every day to protect their fellow citizens from insurgent brutality."
Opening the conference in Kabul, Afghan president Hamid Karzai said: "I remain determined that our Afghan national security forces will be responsible for all military and law enforcement operations throughout our country by 2014."
The conference agreed a communique backing Mr Karzai's target and stating that conditions would be examined with a view to launching the security transition by the end of this year.
Foreign Secretary William Hague told the gathering: "The transition to full Afghan security responsibility should be gradual and determined by Afghan capability, but it should be able to start soon.
"For our part, the UK will continue to provide support and training to the Afghan security forces until that goal is achieved."
Speaking later on the BBC Radio 4 Today programme, he added: "We are trying to make sure that the Afghan state can look after itself in the future so that our forces don't have to be here in the long term.
"I think it is possible for them to be able to run the country and that's why we are saying in five years' time we won't have our combat troops in action here in Afghanistan."
Prime Minister David Cameron has already indicated that he wants the bulk of Britain's detachment in Afghanistan to come home by 2015.
The conference comes in one of the bloodiest periods for international forces since the toppling of the Taliban administration in 2001, with 13 British deaths this month alone.
The deaths included the killing of three British servicemen by a rogue Afghan policeman. Their bodies were flown home today, with hundreds of people lining the streets of Wootton Bassett to pay their respects.
Major James Bowman, Lieutenant Neal Turkington and Corporal Arjun Purja Pun, all of 1st Battalion The Royal Gurkha Rifles, were killed at their base in Helmand province on Monday last week.
Their bodies were repatriated at RAF Lyneham in Wiltshire alongside that of Marine Matthew Harrison, of 40 Commando, who was killed the following day.
The repatriation comes as UK special forces continue a massive manhunt for Talib Hussein who is believed to have carried out the attack last week.
Hussein, 23, shot Maj Bowman in his sleeping quarters in Patrol Base 3 in Nahr-e Saraj district, near the region's capital, Lashkar Gah.
He also fired a rocket-propelled grenade into the base's command centre, killing Lt Turkington, 26, from Craigavon, Northern Ireland, and Cpl Pun as well as wounding four other UK soldiers.
The Union flag-clad coffins carrying Cpl Pun and Lt Turkington were larger than those of Maj Bowman and Marine Harrison and were carried by eight pall-bearers instead of six.
A spokesman for the Ministry of Defence said this was "due to the nature of the injuries sustained by two of the soldiers".
It was the second time in eight months that members of Afghanistan's security forces turned on UK troops.
Five British soldiers were killed and six injured when an Afghan policeman opened fire on them at a checkpoint in Nad-e-Ali in Helmand in November.