The chief of Khalistani Liberation Force (KLF) militant outfit Harminder Singh Mintoo died of cardiac arrest in Patiala central jail on Wednesday, the police said.
"Harminder Singh Mintoo suffered a heart attack in Patiala central jail. He was taken to the government hospital in Patiala where he was declared brought dead by doctors," Punjab Police Inspector General A S Rai said.
Mintoo, aged around 50 years, who was facing several criminal including terror charges, was arrested from the Delhi airport in 2014 after he returned from Malaysia.
He had escaped the Nabha jail along with five other inmates on November 28, 2016, but was nabbed from the Nizammuddin Railway Station in Delhi a day later.
A group of armed men in police uniform had stormed the maximum security jail at Nabha in Patiala district and managed to free six prisoners -- Mintoo, Kashmir Singh, and gangsters Amandeep Dhothian, Vicky Gounder, Gurpreet Sekhon and Neeta Deol.