The Vatican says Pope Francis is stable and that he followed Mass on television after a second night sleeping well at the hospital

Pope Francis remained in a critical condition Sunday and blood tests showed early kidney failure but he remains alert, responsive and attended Mass, the Vatican said, as the 88-year-old pontiff battles pneumonia and a complex lung infection.

Pope Francis remained in critical condition Sunday and blood tests showed early kidney failure but he remains alert, responsive and attended Mass, the Vatican said, as the 88-year-old pontiff battles pneumonia and a complex lung infection.

Pope Francis, who has spent the last two nights in hospital, apologised for missing a mass at the Vatican on Sunday, saying that he was still being treated for bronchitis and thanking his doctors for looking after him.

Valentina Fernandez poses for a picture holding an image of Pope Francis after a Mass to pray for his health at Constitution Square in Buenos Aires, Argentina, Monday, Feb. 24,

Walter Espindola wears a shirt with the image of Pope Francis upon arriving at a Mass to pray for his health at Constitucion square in Buenos Aires, Argentina, Monday, Feb.

On February 24, prayers for Pope Francis continued at Gemelli Hospital, where the Holy Father remains hospitalized. In the St. John Paul II Chapel, Adoration was led by the chaplain at noon, followed by Holy Mass. Let's continue to pray for Pope Francis. pic.twitter.com/ZCZm5mskYg

The 88-year-old pontiff, who has been hospitalized for more than a week, had a restful night after receiving oxygen and a blood transfusion on Saturday, the Vatican said.

Francis, who is being treated at Gemelli hospital for double pneumonia, also had blood tests that revealed mild kidney issues described as under control. The pope also has been receiving high-flow oxygen since experiencing an "asthma-like respiratory crisis of prolonged intensity" on Saturday.

Pope Francis' condition remains critical after developing pneumonia in both lungs earlier this month, but the Vatican said he is showing signs of improvement.

ROME and LONDON -- Pope Francis "rested well, all night long" in the hospital, Vatican officials said in a brief update on Tuesday morning. Francis, 88, has been hospitalized at Rome's Gemelli Hospital since Feb. 14 following a bout with bronchitis.