Col. Almas Kahn, deputy police chief in Helmand province, said on Monday that The attack happened in the Gereshk district yesterday.
Though Kahn blamed the Taliban, the group did not immediately claim responsibility for the attack. Afghan forces have been trying to reduce the number of checkpoints as they are vulnerable to insurgent attacks.
Separately, the Taliban claimed responsibility for firing a series of rockets at Kabul's new parliament building early on Monday. No casualties were reported.
Rockets are occasionally fired at government and diplomatic areas in Kabul, but casualties are rare and the capital has been largely free of deadly attacks for some months.