A weak and breathless Pope Francis thanked people for their prayers for his recovery in a remarkable audio message broadcast Thursday, the first public sign from the 88-year-old pontiff since he was hospitalized three weeks ago with double pneumonia.

Francis' voice, discernible through his labored breaths and in his native Spanish, was recorded Thursday from the hospital and broadcast in St. Peter's Square where the faithful had gathered for the nightly recitation of the rosary prayer.

"I thank you from the bottom of my heart for your prayers for my health from the square, I accompany you from here," he said, his soft voice piercing the hushed square. "May God bless you and the Virgin protect you. Thank you."

The cardinal presiding over the prayer, Cardinal Ángel Fernández Artime, had told the crowd at the start of the service that he had "beautiful news, a beautiful gift" to share. The crowd broke into applause and then applauded again after Francis' final "Gracias." Fernández Artime, for his part, bowed his head as he listened.

Francis has chronic lung disease, and a part of a lung removed when he was younger.

The Vatican has given twice-daily updates on Francis' medical condition but has distributed no photos or video of him since the morning of Feb. 14, when he held a handful of audiences at the Vatican before being admitted to Rome's Gemelli hospital for what was then just a bad case of bronchitis.

The infection progressed into a complex respiratory tract infection and double pneumonia that has idled Francis for the longest period of his 12-year papacy and raised questions about the future of his tenure.

Francis issued written messages from the hospital, but even Vatican officials had been clamoring to hear his voice, saying the pope's calls for peace are particularly needed at a time of such global conflict and war.

More than any pope before him, Francis has mastered the art of informal and direct communication, often recording cellphone videos for visitors to bring home to their communities. For the considerable effort it must have taken, the audio message made clear that he understood the power of his voice, even in its weakened state.

Doctors on Thursday reported that Francis was in stable condition, with no new respiratory crises or fever. He continued his respiratory and other physical therapy Thursday, worked, rested and prayed from the 10th floor papal suite at the hospital.

Given the continued stability of Francis' condition, doctors said they didn't expect to provide a new medical update until Saturday. His prognosis remains guarded, meaning he is not out of danger.

The pope has been sleeping with a noninvasive mechanical mask to guarantee that his lungs expand properly overnight and help his recovery. He has been transitioning to receiving high-flow oxygen with a nasal tube during the day. His routine now includes physical therapy, along with treatment for double pneumonia and respiratory therapy, Vatican officials said.

Francis has been stable for three full days after suffering two respiratory crises Monday.

The pope was supposed to attend a spiritual retreat this weekend with the rest of the Holy See hierarchy. On Tuesday, the Vatican said the retreat would go ahead without Francis but in "spiritual communion" with him. The theme, selected before Francis got sick, was "Hope in eternal life."