A British civilian contractor shot dead by someone wearing an Afghan national security force uniform was a father of two from Kent.
Dave Chamberlain was killed in western Afghanistan alongside two American colleagues by a gunman who turned his weapon against the US-military coalition, sources said today.
Mr Chamberlain, who was in his 40s and from Westgate-on-Sea, was working for the Border Management Task Force, which trains and mentors former Afghan customs officers and border policemen, when he and his colleagues were killed yesterday, a source said.
He said the "green on blue" incident was carried out by a man wearing an Afghan national police uniform who shot at a group sitting outside one of the buildings.
The source said: "One of the Customs and Border Protection officers from America returned fire and killed the assailant."
He said another American national had been taken to hospital with severe injuries and that an Afghan interpreter had also been injured during the shooting.
Mr Chamberlain is believed to have been in Afghanistan since February last year.
The source said: "Everyone involved is in a state of shock. All of us know the dangers but do not expect it to happen like that.
"There are rocket attacks and roadside bombs but one thing you never see coming are the people you are training."
He said he believed the British Embassy in Kabul was making arrangements to have Mr Chamberlain's body repatriated to the UK.
The Foreign and Commonwealth Office (FCO) and the International Security Assistance Force (ISAF) would not confirm the dead man's identity.
The FCO spokesman said: "We can confirm a British national working as a contracted civilian employee for ISAF in western Afghanistan was killed yesterday.
"The next of kin have been informed. We are providing consular assistance."
Five Nato service members have been killed in roadside bombings over the past two days.
Afghan security forces or militants dressed in their uniforms have been killing a rising number of coalition forces, but they have not been specifically targeting contractors working for the coalition, the Associated Press (AP) said.
So far this year, 26 foreign troops have been killed in this type of attack, it said.
All five of the Nato service members were killed in roadside bomb attacks - one on Saturday in the east, and two in the east and two in the south on Sunday.
The deaths bring the number of foreign forces killed so far this year to a total of 247.
Nato also said that it killed a number of insurgents with an airstrike in the Mohammad Agha district of eastern Logar province but would not provide further details.
Afghan officials also reported that four civilians died on Sunday when hundreds of shells and rockets were fired from neighbouring Pakistan, AP said.
The artillery shells hit homes along frontier areas from which insurgents have in the past staged cross-border attacks, according to the report.