Bloodbath at Patrol Base 3 leaves Afghan strategy in doubt

Patrol base 3 was a scene of devastation. The operations room, which had been hit by rocket-propelled grenades was a bloodstained and smouldering ruin. Next to it the briefing room had also burned down following the blast; a charred flag of St George, put up during the World Cup, stood blowing in the ashes.

Bullet holes shredded the brown canvas walls of the tent where the next attack, using a machine gun, had taken place. Gurkha soldiers peered in, shaking their heads and patting each other on the back. A female soldier stood silently as what evidence there was began to be collected, her head in her hands.

The treachery came in the early hours of the morning, one of the victims was still asleep in his bed. The suspected killer, a 23-year-old soldier in the Afghan army with the name of Talib Hussein. The three Gurkhas who died stood no chance. Two of them – believed to be UK nationals – died in the operations room when it came under attack by a rocket-propelled grenade. The lone assailant then opened machine gun fire into a tent where the third, a Nepalese national, was sleeping.

Yesterday's murderous assault on the three men of the Royal Gurkha Rifles regiment at the Nahr-e-Saraj district of Helmand Province sent shockwaves through the military. It was the second such attack by a member of Afghan security forces in under a year. Five British soldiers died last November in another part of Helmand, when an Afghan policeman they were training opened fire.

The repeat incident will fuel fears that the key to the West's "exit strategy", gradually handing over security to the Afghans, will be undermined by an "enemy within". David Cameron spoke by phone to Afghan President, Hamid Karzai, about what he described as an "appalling" incident. "It needs an immediate and urgent investigation and I've discussed that with President Karzai," he said.

As in the previous incident last year, the killing of the Gurkhas was carried out by a lone attacker. The Independent has learned that despite his first name Talib, the suspected killer was from the minority Hazara community which suffered appallingly at the hands of the Taliban when they were in power.

Hussein was regarded by the British troops as so reliable that he was often frequently handpicked as an intermediary to settle any disagreements between them and Afghan forces. He was born in Ghazni province away from areas of Taliban influence and has been in the army for just over a year. Senior officials in the Afghan capital, Kabul, provided references for his security clearance. Yet, last night, in a claim that could not be reliably verified, the Taliban claimed the renegade soldier had surrendered to them after fleeing the British base and was then taken by them to "a safe place".

The killings came just hours after the first Afghan-led military operation against the Taliban – seen as the key part of the West's exit strategy – had successfully been completed in the same area. In the course of the action an Afghan soldier was shot and severely wounded in a Taliban ambush as he fought to protect British Gurkhas alongside him.

The Independent had accompanied Afghan and British troops on the operation – codenamed "Omid Do" – launched to clear Yakhchal, a Taliban enclave, in Nahr-e-Saraj. British and Afghan soldiers spoke of their bewilderment about the slaughter that took place just 10 hours after soldiers from the two armies had fought side by side.

Senior officers flew into PB 3, set in a wilderness of scrubland, in three Chinook helicopters yesterday morning. Brigadier Richard Felton, the head of Task Force Helmand, Lieutenant Colonel Charlie Herbert, in charge of the "partnering" between British and Afghan forces and Colonel Sheran Shah Kobadi, an Afghan brigade commander, met British, Gurkha and Afghan soldiers. The bond between the soldiers, they told those assembled before them, must not be undermined by one act of treachery.

Talib Hussein had been on guard duty at PB 3 at just after 2am Afghan time and took advantage of the mayhem of the immediate aftermath to vanish. A number of weapons were discovered abandoned.

The killings at Nad-e-Ali last year were said to have been triggered by sexual insults and injured pride and this emerged quickly after the attack. There is no such suggestion about the latest killings. Colonel Sheren Shah said: "There is nothing in Talib Hussein's background to suggest insurgent influence. He grew up in Ghazni which has always been against the Taliban. There are 50 schools there, most of them admitting girls. The people who have given their names to his security checks are all responsible people in Kabul, but, they will be arrested and questioned. We shall also try to find out who he might have met when he went on leave.

"To people who say that this shows that cooperation between Isaf ( International Security Assistance Force) and Afghan forces are not working, I would say they are wrong. Yes, there was blood spilt last night and that was terrible. But blood has also been spilt by Afghan and British troops for each other many times and that blood cannot be wiped away from our memories." Col Herbert said: "I lost count of the number of times Afghan warriors came up to me and offered their condolences. We have got a bond which had been formed by fighting together and that will stay strong despite this."

General David Petraeus, the commander of Nato forces in Afghanistan, said: "On behalf of all the troopers of ISAF, I offer sincere condolences to the families and the fellow service members of our fallen comrades."