The health condition of former Uttar Pradesh chief minister Kalyan Singh is critical and he has been put on life support, the Sanjay Gandhi Post Graduate Institute of Medical Sciences (SGPGIMS) said on Wednesday.

"Kalyan Singh ji's health status is critical. He was intubated and put on life-saving support system on Tuesday evening. His clinical parameters are being closely monitored by the expert consultants," the hospital said in a statement.

The senior faculty of the critical care medicine (CCM), cardiology, nephrology, neurology and endocrinology departments are keeping a close watch on all the aspects related to Singh's health, it added.

SGPGIMS Director R K Dhiman is closely monitoring the former chief minister's treatment on a daily basis, the statement said.

Meanwhile, Defence Minister Rajnath Singh visited the hospital and inquired about Kalyan Singh's health from the doctors.

"Visited SGPGI in Lucknow to inquire about health of Kalyan Singh ji. I pray to God for his speedy recovery," he said in a tweet.

BJP veteran Kalyan Singh (89), who is also a former governor of Rajasthan, was admitted to the ICU of the hospital in the evening of July 4 due to an infection and reduced consciousness level.

Earlier, he was undergoing treatment at the Dr Ram Manohar Lohia Institute of Medical Sciences in Lucknow.