Mushtaq died of a heart attack Thursday at the high-security Kashimpur prison, where he had been lodged since August last year. He was arrested in May 2020 in a case filed under the Digital Security Act and charged with spreading disinformation against the government on social media.

"As far as we know Mushtaq collapsed in a washroom of the prison on Thursday evening. Later he was taken to Shaheed Tajuddin Medical college and Hospital, where he was declared dead,” said Gazipur deputy commissioner SM Tariqul Islam.

"The two-member probe panel was formed on Friday night to investigate if there was any negligence during his treatment," he said, adding the committee has been asked to submit its report within two days.

The committee members are Executive Magistrate Mohamamd Wasiuzzaman Chowdhury and Umme Habiba Farzana.

Also read: Writer Mushtaq, arrested under DSA, dies in custody

Mushtaq suffered a heart attack inside his cell at Kashimpur prison on Thursday evening, UNB has learnt.

"He was rushed to Shaheed Tajuddin Medical College Hospital where he was declared dead on arrival," Senior Jail Superintendent Md Gias Uddin said.

Mushtaq's body was handed over to his family on Friday after an autopsy. He was laid to rest that night at Azimpur graveyard, following a namaj-e-janaza in Lalmatia after Isha prayers.

An unnatural death case has been filed at the Gazipur Metropolitan Police's Sadar Police Station in connection with Mushtaq's custodial death.

Also read: Writer Mushtaq's body handed over to family after autopsy

The 53-year-old writer, who published the book "Kumir Chaasher Diary" under the pen name Michael Kumir Thakur, was picked up by Rapid Action Battalion (RAB) personnel from his Lalmatia home on May 2, allegedly for posts critical of the government's handling of the Covid-19 pandemic.

On August 20, he was shifted to Kashimpur prison, Gias Uddin said.

Calls for Mushtaq's release were widespread and sustained throughout his time in prison. Soon after his arrest, more than 300 dignitaries in Bangladesh issued a joint statement demanding his release, including cartoonist Ahmed Kishore.

Also read: Writer Mushtaq's death in custody triggers protests

However, his bail applications were turned down on at least four occasions.

Mushtaq's death triggers protest

Hundreds of students, teachers, and civil society members offered a ghaibana namaz-e-janaza (funeral prayers in absentia) for Mushtaq on Friday in front of the National Museum in Shahbagh.

Also read: Writer Mushtaq laid to rest

However, police baton-charged the left-leaning organisation members who were demonstrating at TSC of Dhaka University that evening over the death of Mushtaq.

At one stage, police fired teargas, forcing the protesters to take up positions in front of the central mosque of Dhaka University. At least 20 protesters were reportedly injured in the clash.