Provincial governor spokesman Dost Mohammad Nayab said the incident has occurred on Monday night in Chinartu district.
According to the source, the infiltrator has poisoned their food first and after the shooting has stolen their weapons and burned the checkpoint and a police vehicle in collaboration with the presumed Taliban allies.
The Taliban have not claimed responsibility for the attack, but Gulam Sakhi Rogh liwanai provincial police chief has confirmed the report.
Only a week ago in a similar insider attack four Taliban infiltrator shot and killed nine colleagues before joining the Taliban with weapons and equipment.
Insider attacks have been a major challenge among the Afghan security forces since there have been repeated instances of police and soldiers going over to the Taliban.