South Korean sex offender Son Jong-woo leaving the Seoul Detention Center after serving an 18-month prison term. (Yonhap)

A 26-year-old man responsible for running one of the world's largest child sexual abuse websites has appealed a two-year prison term sentenced for concealing criminal proceeds, court officials said Thursday.

Son Jong-woo filed the appeal with the Seoul Central District Court on Wednesday from a detention center he was put into last week after the court convicted him for hiding the money he had raised from selling child exploitation materials while operating "Welcome to Video."

Prosecutors had already appealed the sentence.

Son was released in July 2020 after completing an 18-month sentence for running the dark web website inaccessible by regular web browsers, where more than 250,000 videos of minors being sexually abused were uploaded and sold to over 1.28 million users.

Two months before Son's release, his father filed a criminal complaint, accusing the son of hiding criminal proceeds. The move was apparently aimed at preventing him from being extradited to the United States, where he was largely expected to serve a longer prison term.

South Korea's justice ministry has since rejected a US request for Son's extradition.

On July 5, the court found Son guilty of hiding about 400 million won (US$305,000) that he had raised from selling child exploitation materials online by turning them into cryptocurrencies.

He was also convicted of using about 5.6 million won from the criminal proceeds for online gambling.

Son was originally arrested back in March 2018, when the US Department of Justice traced the exchange of cryptocurrency. Law enforcement from across the globe worked together to rescue at least 23 underage victims, and hundreds of people in a dozen countries were arrested for using the website. (Yonhap)