VATICAN CITY — Pope Francis made a surprise entrance Sunday to St. Peter’s Square during a Jubilee Mass for health workers and the sick, marking his first public appearance at the Vatican since leaving the hospital two weeks ago after a life-threatening bout with pneumonia.

The pontiff waved at the crowd of faithful who stood and applauded as he was pushed in a wheelchair unannounced to the front of the altar in the square. Some exclaimed “I see the pope!” as his image first emerged on a big screen showing him passing through the Holy Door before being brought down a ramp to the altar.

“Good Sunday to everyone,” Francis said. “Thank you very much.”

The pontiff’s voice sounded stronger than when he addressed well-wishers outside Gemelli hospital when released March 23, after a five-week stay.

He wore nasal tubes to receive supplemental oxygen, which the Vatican says is being gradually reduced. As he waved and blessed the crowd, his arm movements remained limited — which his doctor said was not related to his illness but to an unspecified trauma suffered before his Feb. 14 hospitalization.

After the Mass, the pontiff greeted some of those who assisted in the service, many who bowed to kiss his hands. He exited the square through the Holy Door.

The pope referred to his experience with illness in the traditional Sunday blessing and in the homily read by an archbishop.

“In this moment of my life I share a lot: the experience of infirmity, feeling weak, depending on the others for many things, needing support,” his homily read. “It is not easy, but ... (we are) grateful to God and to our brothers for the good that we receive, trusting for what is still to come.”