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

Francis’ feeble voice, discernible through his labored breaths and in his native Spanish, was recorded from the hospital and broadcast to the faithful in St. Peter’s Square who 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.”

For anyone used to hearing Francis’ voice, which is often so soft it sounds like a whisper, the audio was an emotional punch to the gut that hammered home just how sick he is.

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 clearly surprised crowd broke into applause and then applauded again after Francis’ final “Gracias.” Fernández Artime, for his part, bowed his head as he listened.

The 88-year-old pope has chronic lung disease and had part of one lung removed as a young man. (AP)