An Afghan official says at least eight members of the security forces have been killed by two other policemen in southern Zabul province.
Gul Islam Seyal, spokesman for the provincial governor, said Saturday that both attackers fled the area after attacking their colleagues late Friday night.
He said the two policemen also took all the weapons and ammunition from the checkpoint in Shinhai district.
Seyal said an investigation is underway to find out what caused the incident or if they had links to insurgent groups.
Insider attacks are not unusual in Afghanistan. In a similar incident in late February, 11 police were shot and killed by another policeman from the same checkpoint in neighbouring Helmand province and the attacker managed to flee.