Pintu, a former Jatiyatabadi Chhatra Dal chief and MP, died after suffering a cardiac arrest at the Rajshahi Medical College and Hospital, doctors said on Sunday.
His family claimed it was a case of ‘premeditated murder’ but jail officials dismissed the allegations.
BNP chief Khaleda Zia, in a statement, condemned what she described as the ‘inhumanity’ of the jail authorities.
“Gross negligence of the jail authorities and disregard for doctors’ advice led to Pintu’s untimely death,” the former prime minister said.
The former MP, known for heading an organised crime syndicate in Old Dhaka and brash behaviour, often made headlines during the BNP-Jamaat-e-Islami alliance’s 2001-6 term for extortion and terrorism.
He was even arrested in one such case while an MP and was sent to jail, but managed to get bail.
In 2013, a special court sentenced him to life in a case over the BDR mutiny, which left 74 people, including 57 army officers dead.
He was shifted to the Rajshahi jail from Narayanganj on Apr 20, a senior jail official said.
BNP’s International Affairs Secretary Asaduzzaman Ripon also blamed the death on the jail authorities.
Speaking to reporters at Naya Paltan in the afternoon, he claimed Pintu had been shifted to Rajshahi “ignoring the High Court’s orders”.
“His condition deteriorated on Apr 25. He didn’t get any treatment,” Ripon alleged. “We don’t believe he died a natural death.”