HERAT, Afghanistan, May 18 (Xinhua) -- At least one person was killed and two others sustained injuries after unknown armed men opened fire on a bus of military hospital in Afghanistan's Herat province Thursday, police said.

Two guys riding a motorbike sprayed bullets on the bus of military hospital in Herat city, capital of the province located about 640 km west of Kabul, police spokesman Abdul Ahad Walizada said.

A staff of the hospital was killed on the spot and two others including a civilian were injured.

The attackers made their good escape, the official said, adding efforts are underway to identify and bring to justice those behind the brutal murder.

No groups or individuals have claimed responsibility.