A U.N. investigator says tens of thousands of North Koreans are being sent to work abroad in conditions that amount to forced labor to circumvent U.N. sanctions and earn foreign currency for the country amounting to between $1.2 billion and $2.3 billion annually by one estimate.

Marzuki Darusman, the special rapporteur on human rights in North Korea, said in a report to the U.N. General Assembly and a press conference Wednesday that the workers earn $120-$150 per month on average, don't get enough food, and are sometimes forced to work up to 20 hours a day.

According to various studies, he said, more than 50,000 North Korean workers are employed in foreign countries, the vast majority in China and Russia but also elsewhere in Asia, Africa, the Mideast and Europe.