Former prime minister Atal Behari Vajpayee's health worsened on Friday with AIIMS doctors putting him on "mechanical ventilation" after his respiratory infection worsened.

"He (Vajpayee) continues to have lower respiratory track infection which has worsened since morning. He has been put on mechanical ventilation in ICU and is being monitored by a team of doctors," Dr Sampath Kumar, head of Cardiac Thoracic Vascular Sciences of AIIMS, said while reading out a brief medical bulletin.

All his basic parametres including blood pressure, liver and kidney functions were normal, Kumar said.

The 84-year-old Vajpayee continues to be in the ICU. His progress is being monitored by a team of doctors, AIIMS Medical Superintendent Dr D K Sharma said in a bulletin earlier in the day.

The doctor had said on Thursday that Vajpayee "is not having fever and his lower respiratory track infection is much better. His condition is stable."