WASHINGTON: Two US men have been jailed for up to 38 years for their roles in an online child pornography ring involving some 500 people worldwide, many of whom personally abused children, officials said Friday.

Thomas Attebury, 40, was sentenced Thursday to 38 years in prison for using "a sophisticated, password-protected Internet bulletin board group, which existed to allow members to meet like-minded individuals with a sexualized interest in children, to discuss that interest and to trade images of child pornography," according to the US Department of Justice.

David Williams, 46, was sentenced to 25 years, while both were also ordered to undergo lifetime supervised release after their prison terms.

"Both defendants pleaded guilty on previous dates to one count of conspiracy to advertise child pornography, one count of conspiracy to distribute child pornography, two counts of advertising child pornography and two counts of distributing child pornography" before a judge in Indianapolis, Indiana, the department said in a statement.

As part of his plea, "Attebury also admitted to the sexual abuse of three minors, one of whom was under the age of 12."

Williams was convicted in 1996 on charges stemming from the sexual abuse of a five-year-old child.

The men were nabbed by "Operation Nest Egg," an inter-agency US probe launched in early 2008 which targeted 26 defendants in the state of Indiana and another 500 located throughout the world for their involvement in the online group.

Twenty-two of those charged in Indiana have been arrested while four remain at large and are known only by their online identities.

Operation Nest Egg to date has led to more than 50 arrests and 39 convictions.

"Numerous members of the Internet-based bulletin board were found to have been personally sexually abusing children, for example Attebury and Williams," the Justice Department said.

Child pornography networks have proliferated with the rise of the Internet, and governments across the world -- notably in Europe and the United States -- have taken steps to crack down on abusers, remove child porn from the Web and punish traders and end users of the illicit material.

BDST: 0920 HRS, 17 July 2010