An Afghan policeman drugged and shot dead 10 of his comrades in the central province of Uruzgan early Tuesday.
Taliban claimed responsibility for the attack.
"The policeman who had connections with armed militants first poisoned his comrades and than shot all of them during the night in a checkpoint," Dost Mohammad Nayab, a spokesman for the governor of Uruzgan, told the DPA news agency.
Weapons and ammunition were missing from the checkpost and a police vehicle was burned following the attack.
The suspect was on the run, said Nayab.
A convoy of police heading for the checkpoint on Tuesday repelled a Taliban attack with no casualties sustained, he said.
So-called "green-on-blue" attacks, when Afghan soldiers or police turn their guns on international troops or colleagues, have been a major problem during NATO's long years fighting alongside Afghan forces.
The killings have bred fierce mistrust among local and foreign forces even as the rate of such incidents has dropped in recent years.
Two US service members were killed in August last year when an Afghan soldier opened fire in southern Helmand province.
| The impact of green-on-blue attacks on Afghan morale
Source: Al Jazeera And DPA