According to the source, the attack took place last night in the Takht-e-Pul district of the southern Afghan province. In total, seven policemen were pronounced dead and four more suffered injuries.
Several militants were also killed in the clashes, although the exact number has yet to be confirmed, the source said.
The latest attack follows in the wake of an incident two weeks ago that left seven other law enforcement officers dead in the same area. During the attack, four insurgents stormed a checkpoint before fleeing with weapons.
The Taliban have not commented on the latest attack.
Armed clashes and bomb blasts continue to impact Afghanistan despite the ongoing peace talks between the Afghan government and the Taliban in Qatar. Both sides have reportedly stated their willingness to work toward a lasting ceasefire, although US officials have reiterated calls over recent days for both sides to reduce the violence.