A police source told the BBC that an infiltrator from the Taliban had allowed militants into the outpost in the regional capital, Lashkar Gah. The infiltrator fled with the Taliban.
Other reports said the infiltrator killed the policemen himself.
A spokesperson for the provincial governor confirmed the attack, but did not provide details.
Local television news reported that the Taliban seized weapons and ammunition from the scene, and that a local hospital had confirmed receipt of at least 11 bodies.
