They said his vital and clinical parameters are stable.

The doctors at the Army's Research and Referral Hospital in Delhi Cantonment said the health of the former president is being closely monitored by a team of specialists. 

His son Abhijit Mukherjee said he visited the hospital on Saturday and his father "is much better and stable than the preceding days".

"Yesterday, I had visited my father in Hospital. With God's grace and all your good wishes, he is much better and stable than the preceeding days! All his vital parameters are stable and he is responding to treatment. We firmly believe that He will be back among us soon. Thank You (sic)," he said on Twitter. "With all your prayers and good wishes, I firmly believe that he will be back among us soon and in good health," he tweeted.

The 84-year-old former president was admitted to the hospital on Monday and was operated upon for removal of a clot in the brain. He is also COVID-19 positive. 

The hospital, in a statement, on Sunday said, "There is no change in the condition of Hon'ble Shri Pranab Mukherjee. His vital and clinical parameters are stable and he continues to be on ventilator support." 

"The health condition of the former president who also has multiple old co-morbidities is being closely monitored by a team of specialists," it said.

Pranab Mukherjee served as the 13th President of India from 2012 to 2017.