Pope Benedict XVI's former diocese in Germany is facing daily allegations of physical and sexual abuse, the head of its new sex-abuse task force says.
"It is like a tsunami," Elke Huemmeler told the Associated Press news agency.
She said about 120 cases had come to light so far in Munich, about 100 of them at a boarding school run by monks.
The Roman Catholic Church has been rocked by scandals involving priests in Germany, Switzerland, Ireland, Austria and the Netherlands in recent months.
Pope Benedict has written a pastoral letter to the Catholics of Ireland, to be read at Sunday Mass, with guidelines on preventing and punishing sexual abuse of children by priests.
It is unknown if the letter includes an apology.
Willey: Vatican ends 'wall of silence'
The Pope has said he hopes the letter will "help in the process of repentance, healing and renewal".
The BBC's David Willey in Rome says that a taboo that has endured for decades has been broken and the Vatican is now taking a much harder line than in the past.
It is recommending a zero-tolerance attitude, adopted by American bishops after widespread cases of sexual abuse of children by priests in the US.
As this will be the first public document published by the Vatican on this potentially explosive subject, there is worldwide interest in what the Pope is going to say, our correspondent says.
The guidelines he will announce will be valid for other countries as well as Ireland.
'Shocked'
Ms Huemmeler spoke to AP as her newly-appointed Task Force on Sexual Abuse Prevention began work in the Munich diocese, backed by Archbishop Reinhard Marx.
Ms Huemmeler said she and colleagues had been "shocked" when the first revelations of abuse cases at the Ettal monastery boarding school, run by Benedictine monks, emerged.
The diocese has not confirmed details of all the allegations, saying investigations are ongoing, the AP reports.
The Vatican recently denounced attempts to link the Pope to a child sex scandal in his former diocese.
The episode dates back to 1980, when he was archbishop of Munich and Freising, and known as Joseph Ratzinger.
The diocese said he had once unwittingly approved housing for a priest accused of child abuse.
However, a former deputy said he - not the future Pope - had made the decision to re-house the priest, who later abused other children and was convicted.
Last year, a damning report into child abuse in the Dublin archdiocese criticised the Catholic Church hierarchy for covering up hundreds of cases going back to the early 1970s.
Until recently, the Vatican has been on the defensive, our correspondent says, protective of priests rather than their victims, and arguing that ecclesiastical courts should decide on suitable punishment for errant clergy.
But victims of clerical sexual abuse argue that they want a full-scale apology from the Pope, in addition to compensation.
They also say bishops should always notify the local police first, not the Vatican, when cases of sexual abuse by clergy are reported to them.
