Vatican City - Pope Francis, who was admitted to the hospital last week, is suffering from pneumonia in both lungs, and the 88-year-old's clinical situation remains "complex", the Vatican said Tuesday.

Francis was admitted to the Gemelli hospital in Rome on Friday with bronchitis after suffering breathing difficulties, and the Holy See has canceled his events until the end of the weekend.

"The laboratory tests, chest X-ray, and the Holy Father's clinical condition continue to present a complex picture," the Vatican said in a statement.

It said a "polymicrobial infection" which has come on top of "bronchiectasis and asthmatic bronchitis, and which required the use of cortisone antibiotic therapy, makes therapeutic treatment more complex".

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"The follow-up chest CT scan which the Holy Father underwent this afternoon... demonstrated the onset of bilateral pneumonia, which required additional drug therapy," it said.

"Nevertheless, Pope Francis is in good spirits," it added.

Francis spent his fifth day in the hospital alternating rest with prayer and reading texts, the Vatican said.

"He gives thanks for the closeness he feels at this time and asks, with a grateful heart, that we continue to pray for him", it added.

The head of the Catholic Church since 2013, Argentine Francis was admitted to the hospital after struggling for several days to read his texts in public.