VATICAN CITY: Pope Francis on Sunday rejected as offensive and unfounded what he called insinuations by the brother of a Vatican schoolgirl who went missing 40 years ago about one of his predecessors as pontiff, Saint John Paul II.

Emanuela Orlandi, the daughter of a Vatican usher, failed to return home on June 22, 1983 following a music lesson in Rome. She was 15 at the time and lived with her family inside the Vatican. Her disappearance is one of Italy's most enduring mysteries.

The case entered a new chapter on Tuesday when her brother Pietro met with Vatican chief prosecutor Alessandro Diddi, whom Francis has given free rein to get to the bottom of the case.

After speaking to Diddi for more than eight hours, Pietro Orlandi appeared on a television programme where he played part of an audio recording with the voice of a man Orlandi said was part of an organised crime group that Italian media have for decades speculated may have been involved in his sister's disappearance.

The voice of the alleged gangster says that more than 40 year ago, girls were brought into the Vatican to be molested and that Pope John Paul knew about it.

Orlandi then said in his own words on the show: "They tell me Wojtyla (Pope John Paul II's surname) used to go out in the evenings with two Polish monsignors and it certainly was not to bless houses".

The comments caused a storm and were condemned by Vatican officials in the past few days before the pope himself entered the fray at his noon address to about 20,000 people in St. Peter's Square.

"Certain that I am interpreting the sentiments of the faithful from all over the world, I express a grateful thought to the memory of St. John Paul, who in these days has been the object of offensive and unfounded insinuations," Francis said.

The mostly Italian crowd broke into applause.

Diddi summoned Pietro Orlandi's lawyer, Laura Sgro, on Saturday. The Vatican said she invoked attorney-client privileges. Sgro told Reuters on Sunday that John Paul did not come up in her conversation with Diddi, adding in a text message: "I have never questioned the sanctity of John Paul II".

Orlandi told Reuters on Sunday by telephone that it was "correct that Francis defended John Paul II". Orlandi added that during the television appearance he was "repeating what others had said. I certainly did not see it myself".

The Vatican's editorial director, Andrea Tornielli, earlier condemned Orlandi's comments as a "sleazy" vilification of the pontiff, who led the Catholic Church from 1978 to 2005 and was declared a saint in 2014.

Cardinal Stanislaw Dziwisz, who was John Paul's secretary throughout his leadership, called Orlandi's actions "ignoble, unrealistic, laughable if they were not tragic, even criminal".

Over the past four decades tombs have been opened, bones have been exhumed from forgotten grave sites and conspiracy theories have abounded in attempts to determine just what became of Emanuela Orlandi.

The case, which has been the subject of on-and-off investigations in Italy and the Vatican, has drawn fresh worldwide attention following the release late last year of the Netflix series "Vatican Girl".

She would be 55 now.