Vatican City (AFP) - Pope Francis on Thursday promised "changes" to the Chilean church to "restore justice" following a child abuse scandal that has come to haunt his papacy.

However in a short letter addressed to 34 Chilean bishops, whom the Argentinian pontiff met in groups from Tuesday to Thursday, he gave no indication of eventual consequences for those suspected of keeping silent about the abuse.

"I thank you for the full availability that everyone has shown to adhere to and collaborate in all the changes and resolutions that we will have to implement in the short, medium and long term, necessary to restore justice and ecclesiastical communion," the pope said in a statement in Spanish circulated by the Vatican.

He said the meetings had been a "frank" exchange about "the grave events that have damaged ecclesiastical communion and weakened the work of the Church of Chile in recent years".

"In the light of these painful events concerning abuses -- of minors, of power and of conscience -- we have gone further into the seriousness of these situations as well as the tragic consequences they have had, particularly for the victims."

The pope said he had asked for "forgiveness from the heart" from the abuse victims, adding that the Chilean bishops expressed their "firm intention to repair the damage caused".

The letter ended with a call for the bishops to create a church which listens to "the hungry, the imprisoned, the migrant and the abused".

- 'Making history' -

The unprecedented summoning of the Chilean delegation is also a chance for Francis to repair some of the damage done during his visit to the country in January, when his defence of controversial bishop Juan Barros caused a public outcry.

The pontiff had strongly defended Barros who has been accused of covering up abuses by Fernando Karadima, another priest, in the 1980s and '90s.

Francis at the time said he was convinced of Barros' innocence and demanded "proof" before he would speak out against him.

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Francis later apologised to the victims, admitting he had made "grave mistakes" after reading a 2,300-page report on the abuse in Chile.

The report's co-author Jordi Bertomeu, who helped lead the investigation, has said the Holy See is "making history", adding that sexual abuse "cannot be tolerated".

"We are waiting for concrete measures in the near future. The pope is a man of his word," he said.

The visit by the Chilean bishops comes two weeks after Francis held private meetings with three victims of Chilean paedophile priest Karadima and promised to adopt "adequate and lasting" measures.

Victims Juan Carlos Cruz, James Hamilton and Jose Andres Murillo broke the silence surrounding Karadima's abuse, in a case that has reverberated through the highest echelons of the Catholic Church.

The trio accused Cardinal Francisco Javier Errazuriz, a key advisor to Francis, of ignoring and helping to cover up the abuses committed by Karadima.

On Thursday, Errazuriz accused the victims of "slander" in an interview with Chile's T13 media.

"I investigated Karadima, I will not say more," he said, adding that Francis had told him "I had always informed him well".

Karadima was forced into retirement in 2011 after eventually being found by the Holy See to have been a serial abuser of minors during the 1980s and 1990s.