Former President Pranab Mukherjee underwent successful brain surgery for removal of clot on Monday.
According to reports from PTI, he is currently on ventilator support at the Army's Research and Referral R&R Hospital in Delhi.
The sources also said that the former President is critical and is on ventilator support.
Defence Minister Rajnath Singh visited the R&R Hospital and enquired about the former president's health.
Earlier in the day, Pranab Mukherjee had informed that he has tested positive for coronavirus and requested people who recently came in his contact to get tested for the virus.
Mukherjee wrote on his Twitter, "On a visit to the hospital for a separate procedure, I have tested positive for COVID19 today. I request the people who came in contact with me in the last week, to please self isolate and get tested for COVID-19."
The octogenarian leader is not the first political figure in India to have been tested positive for coronavirus.
Following his tweet, wishes for an early recovery poured in on Twitter from a large number of people including leaders from across the political spectrum.
President Ram Nath Kovind spoke to Mukherjee's daughter Sharmistha and inquired about his health, the Rashtrapati Bhavan tweeted.
A powerful orator and scholar, he had been a Congress stalwart before he was elected as India's 13th President and served from July 2012 to 2017 in the top post.
"We wish former President Pranab Mukherjee a speedy recovery from Covid," the Congress said on its official Twitter handle.
Abhijeet Mukherjee, Congress leader and the former president's son, tweeted, "I wish my father a speedy recovery! I appeal to all my countrymen to pray for his speedy recovery & good health."
Defence Minister Rajnath Singh visited the R&R Hospital and enquired about the former president's health.
Singh was at the hospital for around 20 minutes.
Union minister Piyush Goyal also wished good health for Mukherjee and said he is confident that the former president will quickly recover from the virus.
Congress leader Abhishek Singhvi said, "Astonishing and matter of concern that former President Pranab Mukherjee tested positive for COVID per press reports. Very active, regular walker, wish him quick recovery and restful convalescence."
Rajasthan Chief Minister Ashok Gehlot too wished Mukherjee a speedy recovery.
"Wishing Sri Pranab Mukherjee a speedy recovery. I am sure he will be out of this sooner than later," said Congress leader Mallikarjun Kharge.
(With inputs from PTI)