Pope Francis said on Sunday that he will wait until Australian justice takes its course before taking a position on Cardinal George Pell, who is under investigation in his homeland over sexual abuse allegations.

But the pope, speaking to reporters aboard the plane returning to Rome form Poland, said Pell, now the Vatican's powerful economy minister, should not undergo a trial by the media or by rumor.

Victoria state Police Commissioner Graham Ashton said on a Melbourne radio station program on Thursday that Victoria police had been investigating allegations against Pell for more than a year.