Pope Francis has denounced the theft of documents containing confidential information on alleged financial shenanigans in the Vatican, calling it a "crime."

In his first public comments on the latest "Vatileaks" scandal to rock the Holy See, the Pope told the faithful in St. Peter's Square on Sunday that those who are trying to undermine his papacy will not succeed and that he will continue to pursue church reforms.

The pope said publishing the documents in two books released last week "was a deplorable act that doesn't help," the Associated Press reported.

The books, "Merchants in the Temple" by Gianluigi Nuzzi and "Avarice" by Emiliano Fittipaldi, describe mismanagement and alleged greed by some Vatican officials.

The theft and publication of the documents appear to indicate a bitter internal struggle between reformers and the old guard in the Roman Catholic Church.

"This sad fact will certainly not divert me from the reform work that we are pursuing with my collaborators and with the support of all of you," the pope said amid cheers from the crowd.

Among the confidential information leaked in "Merchants in the Temple," Nuzzi writes that the cost of sainthood can run up to half a million dollars. The author also tells the story of a monsignor who allegedly broke down the wall of his neighbor, an ailing priest, to expand his apartment.

In the other book, Fittipaldi claims that a children's hospital foundation paid $215,000 for the renovation of the apartment of the Vatican's No. 2 official at the time, Cardinal Tarcisio Bertone, and that nearly $429,000 donated by parishioners worldwide to help the poor was illegally transferred to pay for Vatican administration.

Pope Francis has responded to the scandal by detaining two Vatican insiders thought to be responsible for the leak.

One of those detained is the highest ranking Vatican official ever arrested, Lucio Ángel Vallejo Balda, a Spanish priest with links to Opus Dei. The other was a financial PR, Francesca Chaouqui. Both were members of the influential papal thinktank, Cosea, set up by Pope Francis soon after his election to create the template for far-reaching reform of Vatican finances, according to the Guardian.

Paul Vallely of the Guardian said the current "Vatileak" should be seen differently from the original one which occurred in 2012. That was the time when Vatican whistleblowers disclosed top-level corruption and intrigue in the Roman Curia. The leaks were done by Pope Benedict XVI's butler who wanted to expose the Curia officials doing bad things behind the back of his boss, Vallely said.

However, "Vatileaks 2" is about the scandals that have already been uncovered by Pope Francis's reform teams and which the pontiff has already tackled, Vallely said.

One of the confidential information disclosed was about the former governor of the Vatican, Bishop Guiseppe Sciacca, who allegedly ordered workers to break down a wall in his already luxurious home to steal a room from an elderly priest next door while the man was away in hospital. But this happened before Francis was elected pope in 2013, Vallely noted. Moreover, Pope Francis has already summarily demoted and dismissed Sciacca.

In the case of Cardinal Bertone, who allegedly used 200,000 euros from a children's hospital charity to refurbish his penthouse, Pope Francis has also removed this official from his job as Vatican No 2. Moreover, the Pope has made sure that Bertone's successor will have no direct power over Vatican's purse, the Guardian report said.

Pope Francis has been relentless in his effort to stop corruption in the Vatican. He has appointed new Vatican Bank bosses and a stronger financial regulator. He has created Rome's first independent auditor general and a new finance department led by "tough-guy" Australian cardinal, George Pell, the Guardian reported.

In his address to the faithful on Sunday, Pope Francis underscored that the leaked documents were the result of the reform course that he began and that measures had already been taken to address problems, "with some visible results."