A study into sexual abuse in the Swiss Catholic Church has identified almost a thousand victims and widespread efforts to cover up abuse, researchers at the University of Zurich said Tuesday, warning it was "just the tip of the iceberg".

The year-long inquiry by historians, commissioned by Church authorities, identified 921 victims since 1950 and found that most cases either went unreported or documents containing information were destroyed.

Researchers found that "Church leaders ignored, concealed or minimized most cases of sexual abuse analyzed until the 2000s".

"When they were forced to act, they often did so not by focusing on the people concerned, but to protect the perpetrators, the institution or their position", the report said.

The study, which will be completed by a further three-year research campaign, comes after similar efforts to uncover clerical abuse in other parts of the world.

"It is without doubt just the tip of the iceberg", said Professor Marietta Meier, who led the study along with colleague Monika Dommann.

According to the initial findings, 74 percent of victims were children, while a total of 510 people, almost all men, were found to have committed the abuse.

More than half of the victims were male and almost 40 percent were female, the study found.

The subject "has preoccupied us for a long time now and we are distressed and ashamed by it," Renata Asal-Steger, president of Switzerland's Roman Catholic Central Conference, told a press conference.

"We have missed the point, we gave countless excuses and our actions fell short of what the victims are entitled to," she added.

Asal-Steger emphasized that "it is an important day for the Roman Catholic Church in Switzerland".

"Even though atrocious acts and countless failings within the ranks of the three national organizations of the Catholic Church will be brought to light today, we are grateful."

Swiss bishops said Sunday that they had opened a preliminary inquiry into accusations of a cover-up of sexual assaults within the Church.

It was set up following "allegations made against several emeritus and serving members of the Swiss Bishops' Conference as well as other clergy members in the handling of cases of sexual abuse", the group said in a statement.