"It is with immense sadness that we announce the passing away of R K Pachauri, the founder Director of TERI. The entire TERI family stands with the family of Dr Pachauri in this hour of grief," Mathur said in a statement issued by the TERI.

"TERI is what it is because of Dr Pachauri's untiring perseverance. He played a pivotal role in growing this institution, and making it a premier global organisation in the sustainability space," said Mathur, who succeeded Pachauri at TERI in 2015.

Pachauri was admitted to Escorts Heart Institute in the national capital where he underwent open heart surgery and was put on life support on Tuesday, sources said.

In 2015, Pachauri was accused of allegedly sexually harassing a woman colleague after which he quit the post.