A new report says thousands of North Korean women and girls are being forced to into marriages and sex slavery in China.

An investigation by London-based non-profit Korea Future Initiative (KFI) conducted first-hand interviews over two years with 45 survivors and victims of sexual violence.

KFI claims that although North Korean refugees have long been susceptible to human trafficking due to the dire situation in their homeland, the problem has become worse in recent years due to a “voracious appetite for prostitution in China.” The report says North Koreans are in demand because of the low cost charged for their bodies, which can be as little as $4 for prostitution services and $146 for a wife.

“I was deceived by a broker and sold into marriage for ¥5,000 Chinese Yuan ($720 United States Dollars). I spent six years as a slave,” survivor Park Jihyun said in the report.

The report estimates that up to 200,00 North Koreans have fled into mainland China, mostly female. KFI claims that 60% of North Korean refugees in China are trafficked into the sex trade, with 50% of those forced into prostitution, 30% into marriage, and 15% into cybersex.

Many girls and women are sold multiple times, in a trade which the report says generates $105 million annually for Chinese traffickers.

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The report found that cybersex trafficking is increasingly in demand. KFI found that girls as young as nine years old were forced to perform sex acts in front of webcams live-streaming to paying customers, some of whom are believed to be South Korean men.

The U.S. State Department also reported that girls and young women were being exploited by traffickers who sold them into forced marriages, domestic servitude and prostitution in its 2018 Country Reports on Human Rights Practices on North Korea.

Write to Amy Gunia at amy.gunia@time.com.