Pope Francis remained in critical but stable condition Tuesday, with his blood parameters remaining stable as he works from the hospital while battling double pneumonia, the Vatican said.The Vatican's evening update said the 88-year-old pope underwent a follow-up CAT scan in Tuesday evening to check the lung infection.

The Vatican on Monday announced the start of nighttime prayers for the health of Pope Francis in St. Peter's Square, and invited Romans and others to join in, as the 88-year-old pontiff battled a complex lung infection and complications.

Vatican No.2 Cardinal Pietro Parolin led the first night of prayers in St Peter’s Square for the Pope, who remains in a critical condition in hospital.