North Korea detained a US citizen on Friday, South Korea’s Yonhap news agency reported, saying he was arrested at Pyongyang International Airport on his way out of the country.
This brings the total number of Americans held by the isolated country to three.
The man, a Korean-American in his fifties identified only by his surname Kim, had been in North Korea for a month to discuss relief activities, Yonhap said on Sunday.
The man was a former professor at Yanbian University of Science and Technology (YUST), Yonhap said, citing unnamed sources. YUST, a university in neighboring China, has a sister university in Pyongyang.
An official at South Korea’s National Intelligence Service said it was not aware of the reported arrest.
The Swedish Embassy in Pyongyang said it was aware of a Korean-American citizen being detained recently, but could not comment further. The embassy looks after consular affairs for the United States in North Korea because the two countries do not have diplomatic relations.
North Korea, which has been criticized for its human rights record, has in the past used detained Americans to extract high-profile visits from the United States, with which it has no formal diplomatic relations.
North Korea was already holding two Americans.
Otto Warmbier, a 22-year-old student, was detained in January last year and sentenced to 15 years of hard labor by a North Korean court for attempting to steal a propaganda banner.
In March 2016, Korean-American Kim Dong Chul, 62, was sentenced to 10 years hard labor for subversion.
US missionary Kenneth Bae was arrested in 2012 and sentenced to 15 years hard labor for crimes against the state.
He was released two years later.
At least one other foreigner, a Canadian pastor, is also being detained in North Korea. Hyeon Soo Lim, a South Korean-born Canadian citizen in his 60s, was convicted and sentenced to life in prison in 2015 on charges of trying to use religion to destroy the North Korean system and helping US and South Korean authorities lure and abduct North Korean citizens.