The Vatican on Monday announced the start of nighttime prayers for the health of Pope Francis in St. Peter's Square, and invited Romans and others to join in, as the 88-year-old pontiff battled a complex lung infection and complications.

The Vatican says Pope Francis has showed slight improvement in laboratory tests, and has resumed some work activities, including calling a parish in Gaza City that he has kept in

The Vatican said Pope Francis remained in critical condition Monday but showed slight improvement in laboratory tests and resumed some work.

"The night passed quietly, the pope is still resting," the Vatican said Thursday as there's still no update on when he will be released from hospital.

Pope Francis, who has been in hospital for almost three weeks with double pneumonia, spent another "tranquil" night and is still resting, the Vatican said on Thursday. (Reporting by Alvise Armellini,

By Joshua McElwee VATICAN CITY (Reuters) - Pope Francis, battling double pneumonia in hospital, remained stable throughout the day on Tuesday and did not have any new respiratory crises, the Vatican said.

Pope Francis, battling double pneumonia, had a restful night in hospital, the Vatican said on Wednesday. The 88-year-old pope was admitted to Rome's Gemelli hospital on February 14 with a severe respiratory infection that has required continuously evolving treatment.

Pope Francis, 88, "remained stable compared to previous days" and did not have "episodes of respiratory insufficiency" on Thursday, according to the Vatican.

Pope Francis, who has been in hospital for almost three weeks battling double pneumonia, is in stable condition and is doing some physical therapy, the Vatican said on Thursday.