Taliban spokesman Qari Yousef Ahmadi claimed responsibility for the attack.
Men armed with assault rifles stormed the outpost late Wednesday in Farah province's Khaki Safed district, said provincial police chief Shamsul Rahman Zahid. He says eight members of the Afghan Local Police were killed and two captured.
The attacks first shot a guard who was posted outside then pushed into the compound and opened fire on those inside, said Abdul Khaliq Noorzai, the district administrator. The attackers then made off with their weapons.
The assault happened on the same day that a Taliban suicide bomber on a motorcycle killed at least 10 people, including three American soldiers, at a park in northern Afghanistan.
The attacks appear to be part of an increase in violence at the start of the spring fighting season. During the harsh Afghan winter, snow often blocks roads and fighting dies down.
The Taliban are targeting Afghan and NATO security forces as they fight to assert their power and undermine U.S. efforts to try to build up the Afghan military, which will take the lead in combat responsibility over the next couple of years.