A Saudi policeman, aged 25, was killed in Al Qatif, in the Eastern Province, Al Riyadh newspaper reported.
First Lieutenant Abdulla Badr Mohammed Al Qahtani came under fire as he was about to stop at a traffic light in his official vehicle.
An unidentified man shot him dead near Al Buhari village before fleeing the crime scene.
Security authorities launched an inquiry to identify the killer and bring him to justice, said Eastern Province Police media spokesman Colonel Zeyad Al Ruqaiti.