Doctors have given Pope Francis a "guarded" prognosis as he continues to be treated in hospital for double pneumonia. 

The Pope spent a ninth night in Rome's Gemelli hospital after experiencing an "asthma-like respiratory crisis of prolonged intensity" on Saturday morning. 

Doctors treated the Pope with high-flow oxygen and blood transfusions, and said that he spent the rest of the day in his armchair, as he remains "fatigued". 

"The condition of the Holy Father continues to be critical," a statement from the Holy See press office.

The statement continued, "Today's blood tests also revealed thrombocytopenia, associated with anemia, which required the administration of blood transfusions.

"The Holy Father remains alert and spent the day in an armchair, although he is more fatigued than yesterday. At the moment, the prognosis remains guarded." 

In an update on Sunday morning, the Vatican said Saturday night had been "peaceful". 

Last Friday, doctors said they expected the Pope to remain in hospital all of the coming week and that although he is not "in danger of death," he is not completely "out of danger" yet. 

The Catholic Church continues to ask for prayers for Pope Francis, 88. 

The head of the Catholic Church in England and Wales, Cardinal Vincent Nichols, said in a letter to the Pope that he was praying "you may be given strength and perseverance in these days and continue to bring to the world the joy and compassion which has been so steadfastly at the heart of your ministry". 

"[I] assure you of the prayers of so many here in England and Wales. The prayers of the Catholic community are fervent and heartfelt. Many others, I am sure, are joining in this prayer for your recovery and continued health," he said.