District Police Chief Wali Dad Khan said the explosion occurred today evening.
Roadside bombs have become the deadliest weapons in insurgents' arsenal. In the last year the Afghan National Security Forces have taken over security of the country from international combat troops, who are packing up and pulling out by the end of this year.
Since taking over, their casualty rates have soared. According to government figures as many as 100 police and soldiers are killed each month in Afghanistan.