Sarabjit Singh, who was sentenced 16 years ago over deadly bombings, died in the early hours of Thursday from injuries suffered in an attack on April 26.[break]
"We have added a murder clause to the police complaint," Tariq Mehmood, a police official at Lahore´s Kot Lakhpat police station, told AFP.
The two suspects were taken into custody immediately after last week´s attack.
Pakistani police say Singh was hit with bricks and other blunt objects by two inmates, who have been identified only by single names Aamir and Mudasir.
The motive has been unclear, but police say an initial investigation pointed to an exchange of "hot words" with Singh.
Singh´s lawyer Owais Sheikh said his client had received threats following the execution of a Kashmiri separatist in India. Mohammed Afzal Guru was hanged in New Delhi on February 9 for his part in a deadly attack on the Indian parliament in 2001.
Related story
Christchurch shooter to be charged with 89 murder charges
