U.N. special envoy on North Korean human rights Marzuki Darusman said he was concerned about nine defectors who were reportedly sent to China after they were arrested by Laotian police.
"I am extremely disappointed that the Laos government appears to have abdicated its protection responsibilities in this way and I urge the Chinese authorities not to do the same," he said in a statement.
He stressed his concerns stemmed from fears that defectors could face torture or the death penalty if they're returned to North Korea.
He said the status of the defectors was unknown.
The U.N. Human Rights Council in March set up a commission with a one-year mandate to investigate North Korean rights issues. Advocacy groups say the human rights system in North Korea is often overshadowed by concerns about its nuclear weapons program.
The U.S. House of Representatives adopted a resolution last year that described the North Korean government as the most oppressive in the world.