A 61-year-old man from Hawaii has become the fourth US national removed from Cambodia on suspicion of child sex crimes under an international law-enforcement operation targeting Americans who travel to Cambodia to exploit children for sex.

Richard David Mitchell was charged on Wednesday with engaging in illicit sexual conduct in a foreign country by a court in Hawaii. According to the affidavit, witnesses reported seeing Mitchell engaging in sex acts with a 13-year-old girl on the curb of a street in Phnom Penh in August 2008.

He was initially arrested by Cambodian police, but was returned to the US on September 5, where he was taken into custody by US Immigration and Customs Enforcement (ICE) agents. If convicted, he faces up to 30 years in prison and a fine of up to US$250,000.

"Child sex tourism is a scourge: adults preying on the young and vulnerable to satisfy their dark sexual desires," Wayne Wills, special agent in charge of the ICE Office of Investigations in Hawaii, was quoted as saying on the ICE Web site. "There can be no place for the abuse of foreign children by our citizens."

Mitchell was charged under an initiative dubbed Twisted Traveller. Led by ICE and the US Department of Justice, it specifically targets American sex offenders who travel to Cambodia to have sex with children.

Last week, three US nationals became the first to be charged under the initiative.

If convicted, they face jail terms of up to 30 years for each one of their victims.