VATICAN CITY: Jozef Wesolowski, a former archbishop and papal ambassador to the Dominican Republic, will go on trial on Saturday accused of child sex offences in a case seen as a test of Pope Francis's drive to clean up the church.

It will be the first trial held under rules drawn up by the Argentinian pontiff in an effort to make the clergy accountable for their actions around the world and show that the Vatican is sensitive to widespread anger over repeated abuse scandals.

The 66-year-old former Polish archbishop was "apostolic nuncio", or Vatican ambassador, in Santo Domingo for five years

and was recalled to Rome in 2013 after local media accused him of paying boys to perform sexual acts.

The pope ordered a criminal investigation and he was arrested last September and detained in the Vatican -- the first arrest in the tiny city state related to paedophilia charges.

After his arrest, Vatican inspectors found child pornographic material on his computer.

Wesolowski has already been defrocked by a Vatican tribunal, a rare occurrence and a sign of how seriously the church has taken the accusations against him.

He faces up to eight years in jail if found guilty of abusing a minor and two years for possession of child pornography. Such a sentence would almost certainly be served in Italy rather than the Vatican. Officials have also suggested he could be extradited to the Dominican Republic or Poland.

Looking to restore the credibility of the Roman Catholic Church following a wave of sexual scandals around the world, Francis ruled in 2013 that the Vatican's criminal code could be applied to its employees wherever they lived.

In June, he also approved the creation of an unprecedented Vatican tribunal to judge bishops accused of covering up or failing to prevent sexual abuse of minors.

While groups representing victims of priestly abuse have welcomed the Wesolowski trial, they have said much more needs to be done to clean up the Church and root out wrongdoers.

One group, BishopAccountability.org, says 79 bishops have been accused publicly of sexual wrongdoing, and only four have been defrocked.

The pope will not be in the Vatican when Wesolowski's trial opens. He is visiting three South American countries and has taken much of the Vatican media pack with him.

"It's very important that they do this right and I'm pretty sure that the date was chosen so that there wasn't a big media circus surrounding day one of the trial," said Robert Mickens, editor-in-chief of the Catholic magazine "Global Pulse".

A Vatican official said Saturday's hearing was expected to be taken up by procedural matters, adding that the trial was likely to continue for several months.