A U.S. citizen has been detained in North Korea, according to Martina Aberg, deputy head of mission for the Swedish Embassy in North Korea.

“We have been informed and can confirm that there has been a detention of a US citizen Saturday morning local,” she said.

“He was prevented from getting on the flight out of Pyongyang. We don’t comment further than this.”

Tony Kim, who also goes by his Korean name Kim Sang-duk, was detained on Saturday, according to Park Chan-mo, the chancellor of the Pyongyang University of Science and Technology.

Park said Kim, who is in his 50s, taught accounting at the university for about a month. He said Kim was detained by officials as he was trying to leave the country from Pyongyang’s international airport.

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.

Park said Kim had taught at the Yanbian University of Science and Technology in China before coming to Pyongyang. He said he was informed that the detention had “nothing to do” with Kim’s work at the university but did not know further details.

As of Sunday night, North Korea’s official media had not reported on the detention.

Though no details on why Kim was detained have been released, the detention comes at a time of unusually heightened tensions between the US and North Korea.

Both countries have recently been trading threats of war and having another American in jail will likely up the ante even further. Last year, Otto Warmbier, then a 21-year-old University of Virginia student from suburban Cincinnati, was sentenced to 15 years of hard labour in prison after he confessed to trying to steal a propaganda banner.

Kim Dong Chul, who was born in South Korea but is also believed to have US citizenship, is serving a sentence of 10 years for espionage. Another foreigner, a Canadian pastor, is also being detained in North Korea.

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