The 51-year-old criminal was shot ten times and his body was then dumped into a gutter inside the prison premises, a police officer said.
He was shifted to the Baghpat prison from Jhansi jail late on Sunday for a hearing in a district court.
Bajrangi, whose writ ran large and wide in the eastern part of the state for some three decades, was shifted for hearing in an extortion case filed two years back by former Baghpat legislator Lokesh Dixit.
He was kept in a solitary cell. There were other dreaded mobsters like Vicky Sunehda, Sunil Rathi, also lodged in the same jail.
Bajrangi’s family feared for his life and only 10 days back his wife Seema had requested the judge not to transfer her husband to Baghpat but conduct the hearing through video conferencing.
She alleged that the Special Task Force (STF) of the state police was trying to get Bajrangi eliminated.
Chief Minister Yogi Adityanath ordered the suspension of four prison officials, including the jailor, deputy jailer, following the incident.
He assured that stringent action will be taken against those found guilty.
Bajrangi was arrested from Mumbai’s Malad area by the Delhi Police on October 29, 2009 and has been languishing in jails ever since.
He was an accused in the murder of senior Bharatiya Janata Party leader Ram Chandra Singh and legislator Krishnanand Rai besides being accused of many murders, and extortions.