SEOUL, South Korea -- North Korea has confirmed the detention of an American citizen for alleged acts of hostility aimed at overthrowing the country.

The Korean Central News Agency says officials "intercepted" Kim Sang-Duk at Pyongyang International Airport on April 22.

Wednesday's KCNA dispatch says authorities were detaining Kim and are conducting a detailed investigation into his alleged crime.

It says Kim was invited to Pyongyang University of Science and Technology to teach accounting as a professor.

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The school's chancellor and the Swedish Embassy in Pyongyang earlier gave the information about Kim's detention but the reason for his arrest wasn't known. They used a different spelling of Kim's name.

The North is currently holding at least two other Americans, Kim Dong Chul and Otto Warmbier.

Last year, Warmbier, then a 21-year-old University of Virginia student from suburban Cincinnati, was sentenced to 15 years of hard labor 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 U.S. citizenship, is serving a sentence of 10 years for espionage.

The detention comes at a time of unusually heightened tensions between the U.S. 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