Agarwal, also known as Swami Gyan Swaroop, was on a fast-unto-death for a clean Ganga.
Congress President Rahul Gandhi condoled the death of environmental activist G D Agarwal, saying he sacrificed his life for the Ganga river and vowing to take his fight forward.
"He sacrificed his life for saving the Ganga. Saving the river is equivalent to saving the nation. We will never forget him and we will take his fight forward," Gandhi said in Facebook post.
The Indian Youth Congress said it had also organised a candlelight march over the death of Agarwal who died on Thursday at AIIMS-Rishikesh.