By Joshua McElwee

VATICAN CITY (Reuters) - Pope Francis is resting well as he battles double pneumonia, the Vatican said on Wednesday, with an official adding that he is continuing to eat normally and is able to move around his hospital room.

The 88-year-old pope is spending his 13th day at Rome's Gemelli hospital, the longest hospital stay of his nearly 12-year-old papacy.

"The pope had a tranquil night and is resting," the Vatican said in a one-sentence statement that did not provide further details.

A Vatican official, who did not wish to be named because he was not authorised to discuss the pope's condition, said Francis was alert and continuing his treatments, and was able to eat normally and move about his hospital room.

On Tuesday, the Vatican said the pontiff had remained in critical condition for the fourth day running but was stable and had not had any further respiratory crises.

The pope's prognosis, it said on Tuesday, remains "guarded". But his hemodynamic parameters, a measure of the functioning of his body's circulatory system, were also "stable".

Francis, who has been pope since 2013, is originally from Argentina and is the first Catholic pontiff from the Americas. On Tuesday evening, many in Rome's Argentinian community gathered at the Our Lady of Sorrows Church to pray for him.

"We pray for his health, that he can continue to govern the Church," said Reverend Mario Aler, who referred to the ongoing 2025 Catholic Holy Year. "(Francis) should continue to accompany this important event for the whole Church," he said.

Paraguay's ambassador to the Vatican, Romina Taboada Tonina, who was attending the service, called the pope "a great leader, without a doubt".

"Not only for Catholics, but he is a great political leader as well," she said.

At the Vatican on Tuesday evening, hundreds gathered in St. Peter's Square for a prayer service attended by pilgrims and senior Church figures. The service is being repeated daily this week.

POPE CONTINUES WORK FROM HOSPITAL

Double pneumonia is a serious infection of both lungs that can inflame and scar them, making it difficult to breathe. The Vatican has said the pope's infection is "complex", and caused by two or more microorganisms.

Francis, who has been pope since 2013, has suffered several bouts of ill health over the past two years. He is prone to lung infections because he developed pleurisy as a young adult and had part of one lung removed.

A further update on the pope's condition is expected on Wednesday evening. It may give details from a CT scan the pope received on Tuesday to monitor his pneumonia.

Francis has been working occasionally from the hospital as Vatican business continues apace during his illness. The Vatican announced several new appointments on Wednesday that would have needed the pope's approval.

(Reporting by Joshua McElwee, additional reporting by Claudia Chieppa and Malgorzata Wojtunik, editing by Giulia Segreti, Andrew Heavens and Sharon Singleton)