Vatican City (AFP) - The Vatican said Saturday it has charged five people over a leaks scandal at the heart of the Catholic Church, accusing the alleged ringleaders of forming a "brotherhood of crime".

Magistrates on Friday "notified the accused and their lawyers of the charges filed... for the unlawful disclosure of information and confidential documents," it said in a statement, adding that the trial will begin on Tuesday.

Spanish priest Lucio Angel Vallejo Balda and Italian PR expert Francesca Chaouqui were arrested early this month on suspicion of stealing and leaking classified papers to the media.

Journalists Gianluigi Nuzzi and Emiliano Fittipaldi were questioned following the publication of books containing leaked information which depicted corruption, theft and uncontrolled spending in the Holy See.

Vallejo Balda and Chaouqui were both members of a special commission set up by Pope Francis to advise him on economic reform within the Vatican. The fifth person charged, Nicola Maio, also worked with the now defunct commission.

All five risk up to eight years behind bars in the case stemming from the scandal, which lifted the lid on allegations that charity money was spent on refurbishing the houses of powerful cardinals and that the Vatican bank continues to shelter suspected criminals.

Leaked transcripts of Pope Francis's private conversations, secretly recorded by moles, enraged the Vatican amid concerns the 78-year-old pontiff was struggling to win his battle to assert his authority and change the Church.

- Journalists in papal docks -

The priest and PR whizz -- both of whom are described by Italian media as holding grudges against the Vatican -- "assembled a brotherhood of crime... to illegally divulge information and documents", Saturday's statement said.

While Vallejo Balda, Chaouqui and Maio are accused of pilfering the secret papers, Nuzzi and Fittipaldi are accused of putting pressure on their sources to get their hands on as much classified material as possible, it said.

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It will be the first time in the history of the Vatican that a journalist is going before the pope's magistrates.

Fittipaldi told Italian media he was stunned by the Vatican's move.

"Maybe I'm naive but I believed they would investigate those I denounced for criminal activity, not the person that revealed the crimes," he said.

"I understand they are seriously embarrassed in the Vatican over the things in my book, especially because they could not deny any of it. But I didn't expect a criminal trial."

Chaouqui was released shortly after her arrest, pledging to cooperate, but Vallejo Balda is still in a Vatican cell.

The scandal has revived painful memories of the last time employees aired the centuries-old institution's dirty laundry.

In 2012, Pope Benedict XVI's butler engineered a series of leaks that revealed fierce infighting in the highest echelons of the Catholic Church and allegations of serious fraud in the running of the city state.

He was sentenced to 18 months in prison, before being pardoned by the pope but banished from the Vatican forever.

Nuzzi played a central role in breaking that story, which is widely believed to have contributed to Benedict's shock decision to retire the following year.

The Italian journalist defended himself on Saturday, saying the allegations in his book were "not based on conjecture but authentic documents. And it's for exactly that reason that I'm going to be put on trial".

"It seems no one is interested in the return of an 'inquisition'," he said, referring to brutal trials from the 12th century which sought to silence those who criticised or disagreed with the Church, with interrogators expressly encouraged to use torture to elicit confessions.