British and US troops killed by Afghan 'police' in Taliban show of strength

Deaths of eight women in Nato airstrike another blow to Western efforts to secure the region

The often-strained relationship between the West and Afghanistan has taken another blow after a weekend of violence which saw six Nato troops, including two British soldiers, killed by Afghan forces or insurgents dressed in their uniforms. It was also reported that eight women had been killed in a Nato airstrike in the east of the country.

An effective working arrangement between Afghan forces and Nato troops is seen as vital as the West seeks to hand over security to local forces and sharply reduce the number of its own soldiers by 2014. But a series of incidents – both of Western troops being attacked by local forces and of civilians being killed in Nato strikes – have undermined the relationship.

President Hamid Karzai condemned the latest civilian deaths and said an investigation had been launched.

In the latest violence, an Afghan police officer shot dead four US troops at a remote checkpoint yesterday. It was the second attack by Afghan forces, or militants in military uniforms, against international forces in as many days.

The Associated Press reported that the attack at the checkpoint in Zabul province's Mizan district took place when US troops came to the aid of Afghan police who had come under attack from militants.

The deputy police chief for the province, Ghulam Gilani, said it was unclear why the Afghan police had turned on their US allies or if they had been forced to do so by the militants. "The checkpoint was attacked... then the police started fighting with the Americans. Whether they attacked the Americans willingly we don't know," he said.

The incident followed another on Saturday in which two British soldiers were shot dead. The troops from the 3rd Battalion of the Yorkshire Regiment had gone to the help of a man wearing an Afghan police militia uniform. He claimed to be injured before opening fire at a checkpoint in Nahr-e Saraj, in Helmand Province.

The dead soldiers were named by the Ministry of Defence last night as Sergeant Gareth Thursby, 29, and Private Thomas Wroe, 18. A British soldier killed by a roadside bomb on Friday was also named yesterday. Lance Corporal Duane Groom, 32, of 1st Battalion Grenadier Guards, was born in Fiji and joined the British army five years ago, the MoD said.

Yesterday's deaths took to 51 the number of Western soldiers killed by Afghan colleagues in 36 incidents this year. There have been 12 such attacks in August alone, leaving 15 dead.

Such incidents have impacted on efforts by Western forces to train local police and military. US special forces have suspended training for about 1,000 recruits to the Afghan Local Police, a controversial militia outfit which has been accused of corruption, and the uniform of which the killer of the two British troops was said to be wearing.

"The Afghan National Army has been severely infiltrated by the Taliban and all the screening that is supposed to have been done has failed," said Maj-Gen Dipankar Banerjee, a military analyst with the Delhi-based Institute of Peace and Conflict Studies.

Restrictions at the Combat Outpost Garda in Wardak Province were increased yesterday in the wake of the attacks. All interaction between US and Afghan forces was suspended for 24 hours and the outpost's American commander was prohibited from travelling between the US compound and the Afghan Army compound nearby.

Meanwhile, in a separate incident that will further undermine the relationship between Western forces and Afghans, officials have said that eight women were killed by a Nato air-strike in a remote part of Laghman province. The women were said to have been collecting firewood before dawn when they were killed. Villagers drove the bodies to a provincial capital, where they chanted "Death to America", said local officials. A further seven females, some said to be girls as young as 10, were taken to local hospitals after being injured in the strike.

Nato initially said 45 insurgents and no civilians were killed in the attack but a spokeswoman later said Nato was investigating the claims.

Lt Amy Hession said: "Protecting Afghan lives is the cornerstone of our mission and it saddens us when we learn that our action might have unintentionally harmed civilians."

On Friday, insurgents wearing US Army uniforms attacked the Camp Bastion military base, killing two Marines, wounding nine other people and destroying six Harrier jets.

The Taliban claimed responsibility for the attack and said it had been carried out in revenge for the video insulting the Prophet Muhammad.