Tens of thousands of North Korean inmates of Camp 22, one of the regime's most brutal labour colonies, have disappeared, according to a human rights group that is demanding an inquiry into their fate.

There are fears that up to 20,000 people may have been allowed to die of disease or starvation in the run-up to the closure of the camp last year.

The suspicion has emerged after a report by the Committee for Human Rights in North Korea (HRNK) detailing the situation in penal colonies as Kim Jong-un consolidated his power after taking over from his father, Kim Jong-il who died in 2011. The Washington-based organisation gleans information from defectors, including former guards and the occasional survivor of a prison camp, as well as examining satellite imagery.

It focused much of its attention on Camp 22, a compound sprawled across 770 square miles, making it larger than London. The report discloses that two camps have closed in the past year but that 130,000 individuals are still being held in penal labour colonies.

"Through this vast system of unlawful imprisonment, the North Korean regime isolates, banishes, punishes and executes those suspected of being disloyal to the regime," the report states. "They are deemed 'wrong-thinkers', 'wrongdoers', or those who have acquired 'wrong knowledge' or have engaged in 'wrong associations'."

Detainees are "relentlessly subjected to malnutrition, forced labour, and to other cruel and unusual punishment," the report says, with thousands more forcibly held in other detention facilities. (© Daily Telegraph, London)

Irish Independent