The deceased was identified as Abdus Sattar Peda, 76, hailing from Patuakhali district.
In-charge of DMCH police camp Inspector Bachchu Mia said Sattar was admitted to Shaheed Tajuddin Ahmad Medical College Hospital in Gazipur as he fell ill at Kashimpur High-security Central Jail today.
He was then taken to the DMCH where doctors declared him dead around 5:59pm after examination, he said.
On August 13, 2018, the International Crimes Tribunal sentenced Sattar and four other men from Patuakhali district to death for their involvement in crimes against humanity during the Liberation War in 1971.
On September 6, 2015, police arrested the five war crimes accused from different parts of Sadar upazila in Patuakhali on charges of looting, killing, torturing and arson attack during the Liberation War.
On March 8, 2017, charges were framed against them for violating 15 biranganas, torturing 17 women and vandalising 15 houses.