The incident on Mahinderpal Bittu, who was arrested last year, occurred around 5.15 pm. He was rushed to Civil Hospital at Nabha, where doctors declared him brought dead, an official spokesperson told .
Initial investigations have revealed that Bittu (49), a resident of Faridkot, was attacked by Gursewak Singh and Maninder Singh, who were in jail in a murder case.
Chief Minister Amarinder Singh on Saturday ordered an inquiry into the fatal assault on Bittu.
Additional Director General Prisons Rohit Chaudhary will head the fact-finding committee, which has been asked to submit a report within three days.
The inquiry will be in addition to the mandatory judicial inquest into the murder of the accused, the spokesperson said.
The Chief Minister has ordered beefing up of security in the state in the wake of the attack, while appealing to all communities to maintain peace and not give into rumours.
Those involved in the attack would face punishment for the crime, he asserted.
The sacrilege case relates to the alleged desecration of the Guru Granth Sahib in Bargari village in Faridkot in October 2015. Two people were killed and many others injured in Behbal Kalan village of the district on October 15, 2015, when police resorted to unprovoked firing on hundreds of people protesting the sacrilege.
( With inputs from IANS )