A gunman wearing an Afghan army uniform shot and killed two Nato soldiers at a predominantly British base in Helmand province, Afghanistan.
The attack occurred at a military base in southern Afghanistan, Nato's International Security Assistance Force said.
The attacker, suspected of being a rogue Afghan soldier, was shot dead by Nato soldiers.
The incident took place in Lashkar Gah in southern Helmand, an Afghan security source said.
Britain has around 9,500 troops in Afghanistan, most of them based in the area.
The incident appears to be the latest attack by rogue Afghan security forces on Western troops as tensions between Afghanistan and Nato forces intensify.
Nato troops were recently accused of burning copies of the Koran, which angered Afghans and led to several anti-Nato and anti-US protests.
Animosity increased further after US Staff Sgt Robert Bales, 38, killed 17 Afghan civilians in their homes in southern Kandahar.
That incident severely undermined US relations with Kabul and led to calls for Nato to speed up its exit from the country.
About 70 members of the Nato force have been killed in 42 insider attacks from May 2007 to January 2012, Reuters reported.
Most Western combat forces are due to leave Afghanistan by 2014 and Afghan forces are due to assume responsibility for security.