84-year-old Shukla was airlifted to Medanta Hospital in Gurgaon from Raipur early this morning.
Dr Yatin Mehta, Chairman Institute of Critical Care and Anaesthesiology, Medanta Hospital said, "Shukla is undergoing treatment. He is critical but doctors are treating him".
The former union minister yesterday underwent an operation in Jagdalpur hospital for removal of three bullets he had received in the attack.
Heavily-armed Maoists ambushed a convoy of Congress leaders in Chattisgarh's Bastar district yesterday, killing 27 people including senior Congress leader Mahendra Karma, and injuring Shukla and 31 others.