The survivor, known only as Song, said: "There is a house where women are taken before they are sold. When I arrived, there were many [North Korean] women, but also girls".
A 14-year-old tells how she had been sold into marriage for £2,740. Others describe being starved, imprisoned and abused live on camera in sordid cybersex dens that feed the world's insatiable desire for online porn.
A woman called Ms Choi said: "The man... drove me to his apartment... It was shocking to see [North Korean] girls there. I do not know how old they were... I saw two girls who had not yet developed breasts".
She said she was taken to a room that had a bed in front of a table with a computer and a webcam and was gang-raped by four men.
Yoon Hee-soon, the report's author and a researcher at KFI, a London-based not-for-profit organisation that rescues North Koreans in danger, estimates that the exploitation of North Korean women and girls generates £82 million a year for the Chinese underworld.
"Commonly aged 12 to 29 and overwhelmingly female, victims are coerced, sold or abducted in China or trafficked directly from North Korea," she said.
"Many are sold more than once and are forced into at least one form of sexual slavery within a year of leaving their homeland."
North Koreans are especially vulnerable to the vast network of traffickers and brokers who operate in the knowledge their victims cannot turn to the Chinese police for help.
A pattern of exploitation and slavery for sexual purposes has sprung up across the borders of almost all developing countries bordering or trading with China. At the heart of the problem lies a shortage of women in China and an entrenched national misogyny that commoditises women and views them as inferior, say experts.
"There is a sense that women are property, that they are objects of desire, that they are there to please men and that [still] exists today," said Professor Susan Tiefenbrun, emeritus faculty director at Thomas Jefferson School of Law, who has written extensively on trafficking in China.
China's huge working population, the driving force of its extraordinary economic growth, faces the crippling consequences of the former "one-child policy", created in 1979 and relaxed to a two-child decree only in 2016.
According to United Nations projections, China's 1.4 billion population is likely to decline sharply from as soon as 2023. The policy, combined with the preference for males, has resulted in a gender imbalance that has had a profound impact across southeast Asia.
The Chinese Academy of Social Sciences predicts an excess of 40 million men of marrying age by next year.
This has fuelled the lucrative trafficking industry which lures into China tens of thousands of "brides" from low-income communities in countries including Pakistan, Cambodia, Burma, Vietnam and Laos.
In 2016, Phnom Penh said it had identified 7000 Cambodian women living in forced marriages in China. Anti-trafficking groups say the real figure could be double that.
And as China embarks on its ambitious global foreign investment campaign, the so-called Belt and Road Initiative, the country's toxic sex trade is set to spread even further.
"It will make this trafficking problem worse because the more China gets involved with trade, which will be enhanced by that programme, I think more women will come into China and women from China will be going out from the country," said Tiefenbrun.
CASE STUDY: SOKHA, 19
Sokha (not her real name) was just 19 when a Chinese family from Hunan used brokers to pay her impoverished parents in Cambodia's Kampong Cham province £3000 for her hand in marriage to their son.
She went willingly - if afraid - to help her ailing father and mother after a neighbour, in league with the brokers, won her trust, promising she could send money back home. She even met the prospective groom in advance, who seemed to be a pleasant man.
But when she arrived in China her documents were confiscated and the promised wedding did not materialise.
Trapped in the family's home, she was forced to clean and work all day on their farm without payment. At night, her "husband" proved to be impotent and sexually abused her out of frustration. His mother put pressure on her to have a child, while his father harassed her whenever they were alone.
In desperation, Sokha arranged for a nearby Cambodian woman, also married to a Chinese man, to rescue her, but she was tricked again and sold to another man at a party, who beat and raped her.
Eventually, she found a way to contact her parents. Panicked, they called the initial broker, who demanded the £3000 back and threatened to file a police complaint because she had run away.
"My parents are very poor, from the countryside. They were very scared and had no idea of what was right or wrong. They gave the broker all the information about where I was," she said. She was located and returned to the first family, who this time locked her up.
Sokha's only escape was from a window with an 5.5m drop the other side. A steel pin now holds her spine together where she was horribly injured making the jump.
After medical treatment and 20 days in jail for being undocumented, she was returned to Cambodia. Now 21, she warns other young women about her experience.
