Sarabjit Singh has been shifted to Jinnha hospital and doctors said he was in a critical condition.
Five prisoners attacked Sarabjit and hit him on his head with brick inside the jail over an argument. On death row,
Sarabjit is normally lodged in a separate barrack and the incident took place during lunch time.
Five prisoners, who attacked Sarabjit have been identified and being interrogated.
According to the Pakistan, Sarabjit had illegally crossed into Pakistan from Kasur on August 29, 1990. He was arrested on charges of conducting four bomb blasts in Faisalabad, Multan and Lahore. He is named Manjeet Singh in the FIR and sentenced to death.