QUETTA Seven persons, including an eight-year-old boy, received injuries in a grenade attack in Hub area of Lasbela district, bordering Karachi and located 650km southwest of Quetta, on Tuesday while a bridge was partially damaged in another bomb blast in Kalat. Police while quoting eyewitnesses said two masked bike riders lobbed a grenade at shop in Rind Bazaar on Sakran Road, which exploded outside the shop, resulting in injuries to seven persons. They injured are identified as Deya Ram, Sunil Kumar, Abdul Basit, Baderuddin, Abdullah, Abdul Samad and Shahzad, who were first shifted to Jam Ghulam Qadir Hospital at Hub Bazaar and later to Karachi for further treatment. Meanwhile, a blast caused by a explosive material planted beneath a bridge on Quetta-Karachi National Highway near Kalat town partially damaged the structure. Police reached the spot soon after receiving information and cordoned off the area. And in Quetta, unidentified attackers riding a motorbike hurled a grenade at a government primary school located at Mano Jan Road. The explosion shattered the windowpanes but caused no loss of life. Talking to media, principal of the school, Zahoor Ahmed, said he had received no threatening call or letter from any militant group, adding that more than 200 students currently enrolled in the school were safe. Police have registered separate cases against the unidentified people and started search operation for their arrest.