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.

In an update on Monday, the Vatican has said the pontiff has a “polymicrobial infection” of his respiratory tract, which has required a change in his treatment.

Before his admission last week, the Pope had bronchitis symptoms for several days and had delegated officials to read prepared speeches at events.