Former prime minister and senior BJP leader Atal Bihari Vajpayee on Sunday underwent a "routine checkup" at the AIIMS after he was diagnosed with severe respiratory tract infection a few months back.

Vajpayee spent a few hours at the premier hospital after which he returned back.

"He came in at 11 AM for a routine check-up. He left after a few hours," AIIMS Medical Superintendent DK Sharma said.

The 84-year-old leader, who has now retired from active politics, had spent 26 days in the ICU earlier this year after he was admitted to AIIMS on February 3 with high fever and was discharged on March 1.