Pressure mounted Wednesday for the resignation of an embattled Roman Catholic bishop over the discovery at a seminary of a huge collection of child pornography and photos of candidates for the priesthood engaging in gay sex.

Only if Bishop Kurt Krenn steps down "will an extensive investigation be possible" into the discovery of up to 40,000 photos and many videos, said Helmut Schueller, the ombudsman for victims of sexual abuse at the Archdiocese of Vienna. Schueller called on the Vatican to force out Krenn, 68, who oversees the diocese in St. Poelten, where the seminary is located, 50 miles west of Vienna.

Krenn has been widely criticized for dismissing photos of seminarians kissing and fondling each other as a "schoolboy prank." Officials said other photos showed the students allegedly engaging in sex games with older religious instructors.

In a late-night interview Tuesday on Austrian state television, the bishop said he accepted overall responsibility for what happened at the seminary but insisted the furor was excessive. "Although these things naturally fall into my competence, I had nothing to do with them," he said, calling the matter "an exaggeration."

The pornography collection, which was disclosed this week, has scandalized many people in the overwhelmingly Catholic nation. Church leaders are still trying to heal divisions caused by allegations that the late Cardinal Hermann Groer molested students at an all-male boarding school in the 1970s.

A defiant Krenn said published photos showing seminary students French-kissing each other were taken at the end of a Christmas celebration and were merely traditional "Christmas kisses."

"It had absolutely nothing at all to do with homosexuality," he said in the nationally televised interview, adding that those involved would not be punished.

Schueller rejected that notion Wednesday, telling Austrian radio it was "completely clear that the photos concerned homoerotic encounters" between older priests and young seminarians. The seminary's director, the Rev. Ulrich Kuechl, has resigned, as has his deputy, Wolfgang Rothe.

Krenn, however, has refused to step down despite repeated calls for his resignation and for a criminal investigation to determine whether older seminary leaders used their positions of authority to obtain sexual favors from their young charges.

Many of the photos were taken by an unidentified 33-year-old Polish-born priest who used a digital camera, authorities in the province of Lower Austria said Wednesday. Officials have said most of the images involving children were downloaded from a Web site in Poland.

Krenn, whose close ties to the Vatican led to a visit by Pope John Paul II to his diocese in 1998, was criticized at the time for defending Groer and insisting the cardinal was innocent of pedophilia accusations.