The UNHCR has recently posted a report on the situation of North Korean refugees in northeastern China. The report is written by James D. Seymour. From the Executive Summary:
In the wake of the North Korean famine, which began in 1995, hundreds of thousands of people fled to northeast China. Although many returned and a smaller number went to third countries, many tens of thousands remain. They face two main problems. First is the mistreatment they sometimes receive. China does not recognize them as refugees, or even the legality of their being in the country, so they are forced into an underground existence, making them targets for economic and sexual exploitation. Secondly, Chinese authorities take the position, at least implicitly, that their obligation to return these people to the Democratic People’s Republic of Korea supersedes any obligations they would have under the international human rights covenants and refugee conventions. Thus, many people have been forced back to North Korea against their will, where some have been imprisoned and apparently sometimes executed for the “crime” of leaving the country.
The full report, which is 41 pages long, is here (PDF format).