VATICAN CITY — Pope Francis has defrocked the Chilean priest at the center of the global sex abuse scandal rocking his papacy, invoking his "supreme" authority to stiffen a sentence originally handed down by a Vatican court in 2011. In a statement Friday, the Vatican said Francis had laicized the 88-year-old Rev. Fernando Karadima, who was originally sanctioned to live a lifetime of "penance and prayer" for having sexually abused minors in the upscale Santiago parish he ran.

The "penance and prayer" sanction has been the Vatican's punishment of choice for elderly priests convicted of raping and molesting children. It has long been criticized by victims as too soft and essentially an all-expenses-paid retirement.

The Vatican didn't say what new evidence, if any, prompted Francis to re-evaluate Karadima's sanction and impose what clergy consider to be the equivalent of a death sentence. It said Francis made the "exceptional decision" for the good of the church, and cited the church canon that lays out the pope's "supreme, full, immediate and universal power" to serve the church.

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The statement said the decree, signed Thursday, takes effect immediately and that Karadima was informed of it Friday.

The decision appeared aimed at showing a get-tough approach to sex abuse after a series of missteps by Francis and accusations by a former Vatican ambassador that Francis had rehabilitated a now-disgraced former American cardinal early on in his papacy.

Earlier this month, some of the highest ranking Catholic leaders from the U.S. met with Pope Francis to discuss the priest abuse scandal. At the time, U.S. bishops said Pope Francis "listened deeply from the heart" but they offered few details and no "next steps" in how the church planned to deal with abuse.

While the move to defrock Karadima will be welcomed by Chilean victims as overdue, the decision could spark a religious debate for those who see it as a second punishment for the same crime. Francis' conservative critics might also bristle at another display of raw papal power from the Argentine Jesuit.

Francis sparked a crisis in his papacy earlier this year when he strongly defended one of Karadima's proteges, Bishop Juan Barros, against accusations that he had witnessed Karadima's abuse and ignored it.

Francis had claimed that the accusations against Barros were "calumny" and politically motivated, and he defended his 2015 decision to appoint Barros bishop of a small Chilean diocese over the objections of the faithful and many in the Chilean hierarchy.

After realizing that something was amiss, Francis ordered a Vatican investigation that uncovered decades of abuse and cover-ups by the Chilean church leadership. Francis apologized to the victims and set about making amends, including getting every active bishop in Chile to offer to resign.

To date, he has accepted seven of the more than 30 resignations offered, including that of Barros. It was the second time in a month that Francis has laicized a Chilean priest, after five years in which the Vatican appeared to favor less drastic sentences.

On Sept. 15, the archdiocese of Santiago announced that Francis had defrocked the Rev. Christian Precht, citing the Latin terminology — "ex officio et pro bono Ecclesiae" — on his own authority and for the good of the church.

The decision by Francis to revisit Karadima's sentence and impose the stiffest penalty available to him, with the exception of excommunication, is significant as he battles to gain credibility on the abuse issue.

Francis has said he has "zero tolerance" for abuse, but his record has been shoddy and the Barros fiasco made clear that, at least until he changed course this spring, he was more willing to believe his clerical friends and advisers than victims.

Pollsters have cited the Karadima scandal, which first erupted in 2009, as the tipping point in the Chilean church's progressive loss of credibility among ordinary Chileans.

Juan Carlos Cruz, a survivor of Karadima's abuse who has been a key driver in pushing for justice for victims and an overhaul of the Chilean hierarchy, thanked Francis for taking action against Karadima.

"I never thought I'd see this day," Cruz tweeted. "I hope many survivors feel a bit of relief today."