Security was tightened at the South Korean consulate in Hong Kong on Thursday after media reports that a North Korean, possibly a student, had sought refuge there.
The North Korean is understood to be a member of a delegation that attended an academic competition at a Hong Kong university two weeks ago, the South China Morning Post said, citing government sources in the Chinese-ruled city.
Other media said the North Korean was an 18-year-old student who was attending a mathematics competition and was from a family with a military background.
North and South Korea remain technically at war, and the reports of a possible defection are bound to exacerbate tensions.
Uniformed and plainclothes police were patrolling around the office building near the heart of Hong Kong's financial centre where the South Korean consulate is located. Scores of reporters thronged the building.
Local government and consulate officials declined to comment.
"We are aware of the report," a spokeswoman for the Hong Kong police told Reuters, declining to comment further.
The 57th International Mathematical Olympiad was held at the Hong Kong University of Science and Technology on July 11-12. An all-male team of six took part from North Korea, according to the contest website. The team finished in 6th place.