North Korea has been accused of killing the babies of women who are forcibly repatriated from China.
North Korean guards are said to inflict brutal punishments
The US-based Committee for Human Rights in North Korea (CHRNK) said the women were kept in short-term detention camps where they are either given abortions or their babies are killed at birth .
Between 200,000 and 300,000 North Koreans are believed to have crossed into China in the 1990s at the height of the country's famine.
The Stalinist regime regularly denies abusing the rights of prisoners, and also denies that the prison camps described in the report even exist.
It is not the first time allegations of child killings have been made - a Human Rights Watch report made similar claims last year.
But the CHRNK report, based on the testimony of dozens of escaped prisoners, is one of the fullest accounts to emerge so far.
It paints a picture of detention centres and camps where torture, chronic malnutrition and forced labour are commonplace.
One woman told of being forced to assist injection-induced labours and then watching as a baby was suffocated with a wet towel in front of its mother.
Many former prisoners told of babies buried alive or left face down on the ground to die. They were told by guards this was to prevent the survival of half-Chinese babies.
If fleeing North Koreans are discovered by Chinese police, they are almost always returned home.
China has a treaty with its ally North Korea which obliges it to send refugees back.
The report was compiled by David Hawk, a human rights investigator, who interviewed former North Korean prisoners now living in the South.
The Committee for Human Rights in North Korea, which says it is not affiliated with the US government, said the report did not claim to be comprehensive.
'Animals fared better'
The CHRNK says testimony of a former prisoner of a North Korean gulag from 1967-74 is very similar to contemporary accounts, and indicates that the mistreatment of prisoners has not changed much in the last 30 years.
And the group believes that the harrowing events included in its report are continuing.
"We have every reason to believe this [maltreatment] is still being carried out," Debra Liang-Fenton, executive director of the group, told BBC News Online.
She said the group had been in recent contact with more former prisoners and "the testimony pretty much remains the same".
Methods of torture reported across North Korea's detention system include beating prisoners on their fingertips, the use of miniaturised prison cells, getting prisoners to repeatedly stand up and sit down and forcing them to kneel motionless for hours - a punishment described by one prisoner as more painful than beatings.
One former prisoner at a camp in North Hamgyong province said the highlights of his stay were walks outside, when prisoners could eat plants and grass.
The report's contributors reported a constant lack of food and fights between prisoners over scraps of nourishment. No-one expected to survive long-term detention.
A former detainee at facilities in Onsong and Chongjin said the farm animals ate better.
Those who attempted to escape North Korea's gulags were executed, the witnesses said.
Lee Young-kuk, a former inmate at the Yodok camp in South Hamgyong province, told how one man was executed by being dragged behind a car in front of all the prisoners.
When he was dead, other inmates had to "place their hands on his
Ahn Myong-chol, a former guard at the Haengyoung camp in North Hamgyong province, told the group that between 1,500 and 2,000 prisoners, mostly children, died there each year.
Debra Liang-Fenton said that, despite the endemic human rights abuses, her group supported continued diplomatic negotiations with the North Korean leadership.
But, she added, "this report shows that human rights needs to be part of the agenda".