The Tokyo-based conference said past surveys found two reported cases in 2002 and five in 2012, which weren't verified or intended for disclosure. Those past cases will be investigated, including whether alleged abusers were punished, what punishment they received and how bishops responded to the victims, the conference said in an email responding to inquiries.
The decision comes after Pope Francis convened a bishops' summit in February in response to worldwide scandals involving Catholic clergy. He is expected to visit Japan in November in the first papal visit to the country since John Paul II in 1981.
The Catholic Bishops' Conference in Japan said in its statement that the 2002 survey involved confidential inquiries to the head priest in each diocese, while the 2012 survey was intended as a reference in compiling a manual for internal use, rather than as a fact-finding investigation or to resolve the problem.
It said separate survey on sexual harassment in 2004 also found 17 cases of "coercive physical contacts" mostly by priests and the victims included children. The survey, taken from 110 respondents, also found 10 other cases of sexual harassment, including verbal.
A 62-year-old Japanese man recently came forward, saying he was sexually abused by a priest decades ago when he was at a Catholic boys' school in western Tokyo. There have been other allegations of abuse at different Catholic schools, but the extent of the problem has remained unknown.
"Many of the alleged cases such as coercive physical contacts were forced by priests," the conference said. "We believe there are still a significant number of people who cannot speak up even today, 15 years since the survey."
Japan's Catholic community numbers about 440,000, or 0.3 percent of the population.
This story has been corrected to show one of the church surveys was conducted in 2012, not 2015.
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