The incident has taken place in Spin Boldak district of Kandahar late on Monday night near the Durand Line.
A local security official, speaking on the condition of anonymity, said the policemen were shot dead by one of their comrades who has managed to flee the area following the attack.
The Taliban group has claimed responsibility behind the incident and said the policemen were killed in an attack on a security post.
The group also claimed that the attack was carried out as part of the summer offensive launched by the group under the name of Omari Operations.
This comes as at least 7 policemen serving with the Afghan Local Police (ALP) forces were shot dead by their comrades in this province late last month.
Kandahar is the birth place of the Taliban insurgents however the Afghan security forces have managed to maintain security and stability in this province during the past several months.
The anti-government armed militants have been trying to expand their insurgency activities in this province lately amid deteriorating security situation in the south.