Months after he was cleared of child abuse allegations and walked free from prison, Cardinal George Pell has flown back to the Vatican.

Pell, who previously worked as Pope Francis' finance minister, returned to Rome on Tuesday evening, flying out from Sydney, in his first trip to the Vatican since 2017.

He was pictured in the departure lounge wearing a face shield and appeared to be travelling alone.

Nine News reported NSW Police officers transported him through a private entrance.

Katrina Lee, an aide and church spokeswomen, said Pell would fly from Sydney to Rome on a "private visit".

Earlier Tuesday, Lee told AFP he would be travelling to the Italian capital on Tuesday in a "private" capacity.

"He always said he would be going back to Rome at some stage," she said, while declining to comment on the purpose of his trip.

Under current coronavirus travel restrictions, Australians are barred from leaving the country except for official business or compassionate personal reasons.

It was not immediately clear under what circumstances Pell would have been granted an exception to the ban.

The 79-year-old was forced to return to Australia from Rome in 2017 to clear himself of decades-old allegations of child sex abuse.

At the time, he was the third highest Holy See official, and had been attempting to fight the Vatican's financial struggles.

Pell became the most senior Catholic to be convicted of child abuse crimes against two choir boys in the late 1990s when he was archbishop of Melbourne.

He served 13 months in prison before the High Court overturned his conviction in April this year.

Pell's return to Roma comes just days after Pope Francis fired Cardinal Angelo Becciu amid an ongoing financial scandal.

- With wires

Originally published as Cardinal Pell's sneaky exit from Australia