Karachi- At least four policemen today were injured in a grenade attack targeting a check post on main Shahrah-e-Faisal road in Karachi. According to police and resuce teams, some unknown biker riders hurled a hand grenade on a checkpost located under Nursery bridge on Shahrah-e-Faisal. Police said the blast hurt at least four police personnel as attackers managed to flee from the scene.