The condition of former Uttar Pradesh chief minister Kalyan Singh is unstable, and doctors are closely monitoring him, the Sanjay Gandhi Post Graduate Institute of Medical Sciences (SGPGIMS) here said on Monday.

Singh's clinical parameters are being closely monitored by expert consultants at the hospital, it added.

"The condition of Singh is unstable. After breathing problem, he has been kept on non-invasive ventilation," the hospital said in a bulletin issued this evening.

Earlier in the day, the hospital issued a statement saying, "After he (Kalyan Singh) complained of respiratory discomfort on Saturday evening, oxygen therapy was started. He was put on non-invasive ventilation on Sunday evening due to respiratory worsening."

The senior faculty of Critical Care Medicine (CCM), cardiology, nephrology, neurology and endocrinology are keeping a close watch on all the aspects related to his health, it said.

SGPGIMS director professor R K Dhiman is supervising Singh's treatment on a daily basis, the statement read.

The 89-year-old, who is also a former governor of Rajasthan, was admitted to the ICU of the hospital on the evening of July 4 due to an infection and reduced consciousness level.

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