North Korea has detained a US citizen as tensions between the two countries continue to rise.

The North Korean authorities took lecturer Tony Kim, also known as Kim Sang-duk, into custody on Saturday.

Mr Kim, who taught accounting at Pyongyang University of Science and Technology, was detained as he tried to leave the country from the capital's airport.

According to a university spokesperson, Mr Kim had been attempting to reach China with his wife.

The Swedish Embassy in Pyongyang, which deals with US-North Korean consular affairs, confirmed it was aware of the detention of a Korean-American citizen.

The US State Department also acknowledged it was aware of Mr Kim's detention.

Reasoning behind the one-party state's detaining of Mr Kim remains unknown.

His detention, however, had "nothing to do" with Mr Kim's work at Pyongyang University of Science and Technology, according to an institution spokesperson.

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

Mr Kim's detention takes the number of US citizens stuck in the secretive state to three.

Last year, Otto Warmbier, then a 21-year-old University of Virginia student, 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 US citizenship, is serving a sentence of 10 years for espionage.