By Brandon Lowrey and Dan Whitcomb

LOS ANGELES, Feb 1 (Reuters) - The Catholic Church is withholding documents that could shed more light on sexual abuse by priests, a victims' group said on Friday, a day after the Los Angeles archdiocese released 12,000 pages of files on clergy accused of molesting children.

Representatives for the Survivors Network of Those Abused by Priests, or SNAP, also said they were not content with the punishments of two top clergymen linked to efforts to conceal the abuse from authorities, calling the move "window dressing."

After years of legal battles, the archdiocese made public 124 personnel files on Thursday that were part of a 2007 civil court settlement with more than 500 child sex abuse victims in the biggest such agreement of its kind in the country.

Victims' groups said they believed that the archdiocese was still sitting on more files that could implicate priests and other officials.

"We are woefully disappointed at the documents we have seen coming from the Archdiocese of Los Angeles," said Joelle Casteix, a volunteer regional director of SNAP.

Activists said some of the documents released also appeared to be incomplete.

"I can't believe that's all there is," SNAP member Manuel Vega said, adding that he would like to see Church officials cooperate fully with local and federal prosecutors.

An archdiocese spokesman deferred comment to the organization's attorney, who did not immediately return a call from Reuters.

On Thursday, Archbishop Jose Gomez said he had stripped his predecessor, Cardinal Roger Mahony, of all public and administrative duties. Mahony's former top aide, Thomas Curry, stepped down as bishop of Santa Barbara.

"I find these files to be brutal and painful reading. The behavior described in these files is terribly sad and evil," Gomez said in a statement released by the country's largest Catholic archdiocese.

Thursday's release of 12,000 pages of files came more than a week after Church records relating to 14 priests were unsealed as part of a separate civil suit, showing that Church officials plotted to conceal the molestation from police as late as 1987.

Those earlier documents showed that Mahony, 76, and Curry, 70, both worked to send priests accused of abuse out of state to shield them from law enforcement scrutiny in the 1980s.

UGARTE CASE

Among the documents released on Thursday was the personnel file of Father Jose Ugarte, which contains a 1993 letter to an archdiocese official from a man who wrote that Ugarte began sexually abusing him 10 years earlier, when he was 17.

A document in the file says that in 1994, then-Archbishop Mahony and Ugarte reached an agreement requiring the Spanish priest to "leave the United States and take up permanent residence in Spain" and not to return without the express consent of the archbishop of Los Angeles for seven years. The final outcome in that case was not immediately clear.

Los Angeles prosecutors have said they will review and evaluate the documents. The batch of 124 personnel files includes 82 that have information on allegations of sexual abuse, according to the archdiocese.

The Los Angeles Archdiocese, which serves 4 million Catholics, reached a $660 million civil settlement in 2007 with more than 500 victims of child molestation in the biggest such agreement of its kind in the country, and Mahony at the time called the abuse "a terrible sin and crime."

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