Pope Francis has a “polymicrobial infection” of his respiratory tract that will require his treatment in hospital to be changed, the Vatican said Monday, with tests indicating a “complex clinical picture.

Pope Francis is being treated for a "complex clinical situation" and will remain in hospital for as long as necessary, the Vatican has said. The 88-year-old was admitted to Rome's Gemelli hospital on Friday to undergo treatment and tests for bronchitis.

Pope Francis began a fourth day in hospital on Monday, with the Vatican saying treatment was continuing for a respiratory tract infection and he remained in a stable condition. The 88-year-old pontiff slept well overnight and had eaten breakfast on Monday,