Four police personnel including a DSP shot dead by unknown persons at Saryab Road in Quetta on Wednesday. According to sources, unknown attackers riding on a motorbike opened fire on a police mobile near Government Girls Polytechnic college killing DSP Hasan Ali, constable Sifatullah, Nasrullah and driver Muhammad Taqi. Another DSP Ghulam Muhammad was shifted to hospital where he was reported in a critical condition. The attackers were managed to flee from the scene. Police have cordoned off the area after the incident.