A British soldier was shot dead and six others injured by an attacker wearing the uniform of the Afghan National Army at a joint military base in southern Afghanistan, military officials said Tuesday, DPA reported.
The attack took place on Monday at a patrol base in the Greshk district of southern Helmand province.
A press officer at the Afghan military's 215th Corps in Helmand, Mohammad Rasool Zazai, said the attacker was also killed "when British troops returned fire."
However, the BBC quoted Afghan defence officials as saying that the attacker was killed by Afghan national security forces as he tried to escape after killing the British soldier.
Taliban spokesman Qari Yousuf Ahamdi claimed responsibility for the attack, saying the British soldier was killed by one of the group's sleeper agents.
"An infiltrator mujahid (freedom fighter) tasked by Islamic Emirate (the official name of the Taliban movement) has killed eight foreign invaders in Greshk district," he said in an email statement.
The Taliban are known to exaggerate the number of casualties they inflict. The BBC, meanwhile, said it was told by Afghan officials that the attacker was a soldier, who was not linked to the Taliban.
"Insider attacks" - killings of foreign soldiers and civilian contractors by Afghans in uniform - have spiked dramatically since last year.
According to the NATO-led International Assistance Force (ISAF), there were 47 incidents - of which two are still under investigation - in which members of the Afghan army or police attacked members of US and NATO allied forces and contractors in 2012.
Sixty-two of the victims died, most of them US soldiers. At least two-thirds of the incidents took place in southern Afghanistan, with a few incidents in the east and the west. There were no incidents of insider attacks in the north.
By contrast, there were only two deaths a year attributed to "insider attacks" in 2007 and 2008, followed by 10 troop fatalities in 2009 and 20 in 2010.
In some cases, militants donning Afghan army or police uniforms have attacked foreign troops. However, most of the incidents have been attributed to members of Afghan security attacking out of anger or frustration, and without any Taliban links.
In some cases, Taliban infiltration of the soldiers has been recorded.
There has also been a dramatic rise in the Afghan security forces killing their own comrades-in-arms, mostly due to infiltration.