GHOTKI - At least six persons were injured when unknown gunmen opened fire at a passenger bus here on Sunday. The incident took place at National Highway where armed accused signalled to stop a passenger bus and when the driver didn't stop they sprayed bullets at the vehicle. As a result, six passengers were injured. The assailants managed to flee after committing the crime. The injured were shifted to Sheikh Zayed and District Hospital Mirpur Mathelo for treatment.