Pope Francis, who was admitted to hospital last week, has developed pneumonia in both of his lungs, the Vatican announced on Tuesday, adding that the 88-year-old was in "good spirits."

"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.

Francis was admitted to Rome's Gemelli hospital last Friday for bronchitis, but the Vatican on Monday said it was changing his treatment following tests.

It said Tuesday that 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."

"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.

The pontiff had part of his right lung cut away when he was 21, after developing pleurisy that almost killed him.

The Vatican had already cancelled a papal audience on Saturday and said he would not attend a mass on Sunday, although it has yet to announce plans for his weekly Angelus prayer, which is usually held on Sunday.

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

Francis spent his fifth day in 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.

Vatican spokesman Matteo Bruni had earlier told reporters Francis had eaten breakfast and read some newspapers.

Pilgrims pray

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

It is latest of a series of health issues for the Jesuit, who has undergone hernia and colon surgery since 2021 and uses a wheelchair due to pain in his knee.

Among the pilgrims and tourists gathered in Saint Peter's Square on Tuesday morning, many said they were praying for the pope's recovery.

"I hope that he's getting better soon," Birgit Jungreuthmayer, a 48-year-old Austrian tourist, told AFP.

"Pope Francis is touched by the numerous messages of affection and closeness he continues to receive," the Vatican said on Monday.

Active schedule

Despite his health troubles, Francis remains a very active pontiff, with a busy weekly schedule and regular overseas trips.

In September 2024, he completed a four-nation Asia-Pacific tour, the longest of his papacy by duration and distance.

A source within the pope's entourage had told AFP Monday that Francis was admitted after a "very busy" two weeks, during which "he was weakened" — but insisted there was no alarm.

Francis followed last Sunday's mass on television from hospital and sent a written address for the Angelus.

"I would have liked to be among you but, as you know, I am here at the Gemelli hospital because I still need some treatment for my bronchitis," Francis wrote.

The Jesuit has left open the option of resigning if he became unable to carry out his duties.

His predecessor, Benedict XVI, stunned the world in 2013 by becoming the first pope since the Middle Ages to step down, citing his ailing health.

But in a memoir published last year, Francis wrote that he did "not have any cause serious enough to make me think of resigning."

Stepping down is a "distant possibility" that would be justified only in the event of "a serious physical impediment," he wrote.

In an autobiography published last month, he said that despite his ailments, "I carry on."

"The reality is, quite simply, that I am old," he said.