They said the 89-year-old Congress leader had a fever on Monday and had recovered, but he turned weak and was on fluids.
The former PM was admitted to the cardioneuro unit of the AIIMS and is under the care of a team of cardiologists led by Dr Nitish Naik.
The Congress said the former PM is stable and is undergoing routine treatment. “There are some unsubstantiated rumours with regards to former PM’s health. His condition is stable. He is undergoing routine treatment. We will share any updates as needed. We thank our friends in media for their concern,” AICC secretary Pranav Jha tweeted after he was flooded with queries about Singh’s health.