Pope Francis remains stable in hospital and a recent chest scan confirmed improvements in his condition, the Vatican said on Wednesday, in a further sign of progress as the 88-year-old pontiff battles double pneumonia.

A chest X-ray has confirmed improvements in Pope Francis' condition in his fourth week in the hospital for treatment of double pneumonia, the Vatican said Wednesday.

Pope Francis marked the 12th year of his pontificate Thursday while still recovering from lung infection. The anniversary is a public holiday at the Vatican but no events were planned to celebrate the occasion.