The Vatican quoted Francis as expressing personal "sorrow" in his homily at a private Mass with six victims for the "sins and grave crimes" of clerical sex abuse against them.
Francis pledged "not to tolerate harm done to a minor by any individual, whether a cleric or not," and promised that bishops "will be held accountable."
"I beg your forgiveness, too, for the sins of omission on the part of Church leaders who did not respond adequately to reports of abuse made by family members, as well as by abuse victims themselves," the pope said.
Francis noted the abuse caused some victims to resort to addictions, or even suicide.
Also Read
"These deaths of these so beloved children of God weigh upon the heart and my conscience and that of the whole church," he said.
Advocacy groups for clerical abuse survivors have denounced the Vatican repeatedly for failing to fire or otherwise discipline bishops and other prelates who routinely shuffled known pedophile priests from parish to parish without alerting parishioners to the danger.
A German survivor advocacy spokesman, Norbert Denef, called today's meeting "nothing more than a PR event." Vatican spokesman the Rev Federico Lombardi said two Irish, two British and two German victims met with the pope. The three men and three women who had been sexually abused as youths by clergy met privately for about a half-hour each with Francis at his Vatican residence.