At least eight members of the Afghan security forces were killed by two of their colleagues in the southern Zabul province late on March 10, Afghan officials say.
Gul Islam Seyal, spokesman for the provincial governor, said on March 11 that both attackers fled the area in a police vehicle after killing their colleagues in the Shinkai district.
He said the two attackers also took all the weapons and ammunition from the checkpoint.
Seyal said an investigation is under way to find out if the two have links to insurgent groups.
Haji Asadullah Kakar, a Zabul provincial council member, said the attackers had joined the Taliban. Kakar said that it appeared the attackers already had connections with the militant group.
Insider attacks are not unusual in Afghanistan.
In a similar incident last month, 11 police officers were shot and killed by another policeman from the same checkpoint in neighboring Helmand province.
Separately on March 11, in eastern Khost province, a suspected suicide bomber was shot and killed by security guards near the entrance to an airport, said General Faizullah Ghyrat, provincial police chief in Khost.
Based on reporting by AP and dpa