VATICAN CITY — Addressing the clerical abuse scandal from the heart of the Roman Catholic Church, Pope Benedict XVI begged forgiveness Friday from victims and promised at a Mass to "do everything possible" to protect children.

While symbolic, Benedict's pledge failed to satisfy victims groups who said promises were useless without a clear-cut action plan to root out pedophile priests, expose the bishops who protected them and change the Vatican policies and culture that allowed abuse to continue.

His comments came during a Mass celebrated by 15,000 priests at St. Peter's Square marking the Vatican's Year of the Priest — a year marred by revelations of hundreds of new cases of clerical abuse in Europe, Latin America and elsewhere, as well as cover-ups by bishops and evidence of long-standing Vatican inaction.

It was the first time Benedict had spoken of the crisis from St. Peter's Basilica, the center of the church.

Benedict implied the devil was behind the timing of the scandal, saying the Year of the Priest was supposed to have been a year in celebration of the priesthood and encouragement for new vocations.

"It was to be expected that this new radiance of the priesthood would not be pleasing to the 'enemy' "; he would have rather preferred to see it disappear, so that God would ultimately be driven from the world," Benedict said in his homily, to applause from the gathered priests.

"And so it happened that in this very year of joy for the sacrament of the priesthood, the sins of priests came to light — particularly the abuse of little ones," he said.

"We, too, insistently beg forgiveness from God and from the persons involved, while promising to do everything possible to ensure that such abuse will never occur again," he said.

Benedict's comments were similar to those reported by the Vatican during his private meeting with abuse victims in Malta in April, during which the pontiff had tears in his eyes as he heard the stories of men molested by priests as children.

The pope also made similar statements last month en route to Portugal, in which he acknowledged that the "sins from within the church" were responsible for the scandal, not the media or some outside anti-Catholic lobby.

The pope also begged forgiveness from victims in his March letter to the Irish faithful.

However, Friday's homily seemed to wrap up those points in a single message — directed at priests who came to Rome from around the world to support the pontiff and the priesthood itself amid the scandal.

Vatican officials and the priests themselves said they had never seen such a large gathering of clergymen, who all donned white vestments to concelebrate the Mass from their seats in the piazza and renew their ordination vows. Some sported sun hats and others draped their national flags over their shoulders, giving a bit of unusual color to the Vatican's normally formal Masses.

In his homily, the pope pledged that in admitting men into the priesthood and forming them as clergymen "we will do everything we can to weigh the authenticity of their vocation and make every effort to accompany priests along their journey, so that the Lord will protect them and watch over them in troubled situations and amid life's dangers."

Victims groups who had been hoping for a papal mea culpa and clear-cut action plan to protect children weren't satisfied.

"A promise is nominally more helpful than an apology. But promises are usually easy to make, hard to keep and broken often if there's no oversight or penalties," said Barbara Blaine, president of the U.S. victims group SNAP, the Survivors Network of those Abused by Priests.

Another group,, said the pontiff's remarks were both a disappointment and a squandered opportunity in that he only prescribed an internal step: better screening for priests.

It called for him to tell his bishops to do more: stop opposing legislation to extend statutes of limitations so victims can seek justice from abusers; post information about known abusers on diocesan websites and for the Vatican office that handles abuse cases to do the same.

"Once again, the pope focused only on wayward priests, and he once again minimized the sodomizing and abuse of helpless children by calling it a 'sin,' " the group said in a statement.

"He said nothing about the core problem: the Vatican's policies and corrupt culture that encouraged bishops worldwide to cover up thousands of child sex crimes."

Benedict's own legacy has been tarnished by the scandal. As archbishop of Munich in the 1980s, he approved therapy for a suspected pedophile who was allowed to resume pastoral duties while being treated. The priest, the Rev. Peter Hullermann, later was handed a suspended sentence for molesting a boy.

In addition, Benedict's legacy at the Vatican office that dealt with sex abuse has come under scrutiny.

Benedict said the scandal had shown the need for a purification of the church.

"Had the Year for Priests been a glorification of our individual human performance, it would have been ruined by these events," he said. "But for us what happened was precisely the opposite: We grew in gratitude for God's gift."

A Spanish priest who attended Friday's Mass, the Rev. Davide Torrijus, concurred.

"We have all suffered during the Year of the Priest" because of the scandal, he said. "It was good for the pope to show also the positive aspects — gratitude for the gift."