Three Nato soldiers killed by a gunman in a police uniform in southern Afghanistan were British, the Ministry of Defence has said.
The gunman was injured and later detained, according to Nato.
More than 20 foreign personnel have been killed in so-called rogue shootings this year.
Members of the Nato-led Isaf force are training their Afghan counterparts in preparation for a full handover of responsibility for security by 2014.
Observers say the rogue shootings have eroded morale among foreign forces.
"An individual wearing an Afghan National Civil Order Police uniform turned his weapon against International Security Assistance Force service members in southern Afghanistan today, killing three service members," Isaf, Nato's force in the country, said in a statement on Sunday.
Public opinion against the foreign forces in Afghanistan was inflamed by revelations, in February, that US troops burned copies of the Koran at a base in Afghanistan - reportedly by accident.
The shooting of 16 Afghans by a US soldier in March has also created resentment.
