Three Americans, two soldiers and a civilian, were killed in Afghanistan yesterday when a man in an Afghan army uniform turned his weapon on them in the eastern province of Paktika, the Nato-led force said.

So-called insider attacks by Afghan soldiers on their Nato-force allies have become an increasing problem over the past year or so, threatening to undermine already waning support for the war among Western nations sending troops.

Last year, a surge in such attacks prompted Nato to temporarily curtail some joint operations with Afghan government forces.

The three Americans were shot dead by the man following an argument, the Paktika provincial governor’s spokesman Mukhlas Afghan said, adding that three other Americans had been wounded.

The attacker was himself shot dead soon after opening fire, the spokesman said.

“Two US International Security Assistance Force service members and one US civilian were killed today when an individual wearing an ANA uniform turned his weapon against (them),” a statement from Afghanistan’s Nato-led force said.

A previous statement had said all three were soldiers.