Pope Francis's condition continues to be "critical" after suffering a "prolonged asthma-like respiratory crisis" earlier on Saturday; BBC reported citing a Vatican statement.
The pontiff is "more unwell than yesterday" and had received blood transfusions, the statement said.
The Vatican said the 88-year-old was alert and in his armchair, but required a "high flow" of oxygen and his prognosis "remains guarded".
The Pope is being treated for pneumonia in both lungs at the Gemelli Hospital in Rome.
The blood transfusions were deemed necessary due to a low platelet count, associated with anaemia, the Vatican said.
Mentioning that his condition remains critical, the statement said: “The Pope is not out of danger”.
"Pope continues to be alert and spent the day in an armchair even if he was suffering more than yesterday," the statement added.
The Pope has asked for openness about his health, so the Vatican has begun releasing daily statements. The tone, and length, of the announcements has varied, sometimes leaving Pope-watchers to attempt to read between the lines.
But this is by far the starkest assessment yet and it is unusually detailed. It declines to give any prognosis.
It comes just a day after doctors treating the Pope said for the first time that he was responding to medication, although they were clear that his condition was complex. They said on Friday that the slightest change of circumstance would upset what was called a "delicate balance".
"He is the Pope," as one of them put it. "But he is also a man."
The Pope was first admitted to hospital on 14 February after experiencing difficulties breathing for several days.
He is especially prone to lung infections due to developing pleurisy - an inflammation around the lungs - as an adult and having part of one of his lungs removed at age 21.
During his 12 years as leader of the Roman Catholic church, the Argentine has been hospitalized several times including in March 2023 when he spent three nights in hospital with bronchitis.
The latest news will worry Catholics worldwide, who are following news of the Pope's condition closely.
It is a busy Jubilee year for the Catholic Church with huge numbers of visitors expected in Rome and a major schedule of events for the Pope. He is not known for enjoying being inactive. Even in hospital, his doctors say he went to pray in the chapel this week and had been reading in his chair.
But even before the latest setback, the Vatican had said he would not appear in public to lead prayer with pilgrims on Sunday, meaning he will miss the event for the second week in a row.
Well-wishers have been leaving candles, flowers and letters for the Pope outside Rome's Gemelli hospital all week. There was no change outside St Peter's Basilica in the Vatican on Saturday evening, however, with no crowd gathering.
But people passing through the square said they were following the news.
"We feel very close to the Pope, here in Rome," one Italian man told the BBC. "We saw the latest, and we are worried."
Bd-Pratidin English/ AM
