The Vatican said Friday it had asked the Mexican founder of the conservative order Legionaries of Christ to renounce celebrating public Masses and live a life of "prayer and repentance" following its investigation into allegations he sexually abused seminarians.

The Legionaries said in a statement that the Rev. Marcial Maciel, while declaring himself innocent of charges spanning several decades, accepted the Vatican decision "with faith, complete serenity and tranquility of conscience."

Pope Benedict XVI approved the sanctions against Maciel — making it the first major sexual abuse disciplinary case he has handled since taking office last year. The move was first reported Thursday by the U.S. newspaper National Catholic Reporter.

Victims of clerical sex abuse hailed the decision.

"Maciel is the most powerful Catholic official to ever face Vatican sanctions for child sexual abuse," said David Clohessy, national director of the Survivors Network of those Abused by Priests, a U.S. victims' support group.

However, the group said it hoped the Vatican would go further by defrocking Maciel.

The case is significant because Maciel is one of the most prominent Roman Catholic Church officials disciplined by the Vatican for alleged involvement in child sexual abuse. It is also noteworthy because Maciel was so warmly regarded by Pope John Paul II.

Benedict's approval of the sanctions showed that he is not beholden to John Paul's legacy when it comes to dealing with what he once called the "filth" in the Catholic Church — a widely understood criticism of clerical sex abuse.

Since 1998, the Vatican's Congregation for the Doctrine of the Faith, which Benedict headed before he became pope, has been investigating allegations by former seminarians that Maciel sexually abused them decades ago.

Nine former seminarians first accused Maciel in 1996 of having abused them when they were boys or teenagers during the 1940s to 1960s. Later, other alleged victims came forward.

The Vatican did not say specifically whether it found the abuse allegations against Maciel to be true. And it said that because of Maciel's age and ill health — he is 86 — it decided against a full-fledged church trial, or "canonical process."

Instead, it said the congregation had "invited the priest to a reserved life of prayer and repentance, renouncing every public ministry."

But such a serious sanction against as prominent a churchman as Maciel — which would prohibit him from celebrating Mass and other sacraments in public — is a clear indication, some say, that the Vatican found at least some validity to the charges.

The Legionaries said Maciel considered the Vatican decision "a new cross that God, the Father of Mercy, has allowed him to suffer and that will obtain many graces for the Legion of Christ."

Maciel and the Orange, Conn.-based Legionaries strongly denied the allegations in the past.

"Before God and with total clarity of conscience, I can categorically state that the accusations brought against me are false," Maciel said in a 2002 statement. "I never engaged in the sort of repulsive behavior these men accuse me of."

The order, which shares John Paul's conservative views, is one of the fastest-growing religious orders in the church, with some 600 priests and 2,500 seminarians in 20 countries in North and South America, Europe and Australia.

It was well-regarded by John Paul in particular because of its loyalty to church teaching and its success in recruiting priesthood candidates.

In January 2005, John Paul hailed Maciel for his "paternal affection and his experience." A few months earlier, the late pope praised Maciel on the 60th anniversary of his ordination, citing his "intense, generous and fruitful" priestly ministry.

The Vatican statement expressed gratitude for the work of the Legionaries, which Maciel founded in Mexico City in 1941.

The Rev. Jim Martin, associate editor of the Jesuit magazine America, said it was hard to overestimate the impact that the sanctions would have on the Legionaries.

"The distinctive (spirit) of the order comes from the founder," Martin said. "His life is studied, his words are quoted, his picture and statues are everywhere. Any critique of the founder, especially one that's so serious, is a huge mark against the order."

The Vatican investigated Maciel in the 1950s for alleged drug use, trafficking and misuse of funds but not for sexual misconduct. He was suspended from his duties as head of the order then reinstated after being cleared of all allegations.