The JaSaD leader died at a Dhaka hospital on Friday morning, his family said
The war crimes tribunal was investigating the allegations against 90-year-old Amjad Ali.
He was moved to the Dhaka Medical College and Hospital on Aug 27 from the central jail after he complained of chest pain.
Ali died in the afternoon, said Assistant Sub-Inspector Sentu Chandra Das of DMCH Police Outpost.
“War crimes charges against him were being investigated,” tribunal’s Prosecutor Zead Al Malum told bdnews24.com.
Police arrested Ali and one Riaz Uddin from Mymensingh’s Phulbarhia on Aug 11 following the tribunal’s orders.
Ali was injured after a prison van transporting them to Dhaka met with an accident.
The tribunal ordered them into jail the same day after treatment.