North Korea yesterday confirmed the arrest of a US professor for trying to "overturn" the regime, as tensions spike between the isolated nuclear-armed nation and Washington.

Kim Sang-Duk, or Tony Kim, became the third American held in the North when he was detained at the capital's airport on April 22 as he tried to leave the country, after teaching for several weeks at an elite university.

In the North's first confirmation of the professor's detention, the official Korean Central News Agency (KCNA) said he had been held for "committing criminal acts of hostility aimed to overturn the DPRK", using an abbreviation for the country's official name.

It added that Kim was "under detention by a relevant law enforcement body which is conducting detailed investigation into his crimes".

The confirmation of Kim's detention comes as Pyongyang issues increasingly belligerent rhetoric in a tense stand off with the administration of new US President Donald Trump over its rogue weapons programme.

Kim had been teaching accounting at the Pyongyang University of Science and Technology (PUST), which said last month that the professor had been held.

The school -- founded by evangelical Christians from overseas and opened in 2010 -- is known to have a number of American faculty members and pupils are generally children from the country's elite.

In a statement in late April the university said the arrest was "not connected in any way with the work of PUST".

It added that the Swedish embassy in Pyongyang -- which handles issues involving US citizens as Washington has no diplomatic ties with the North -- was "actively involved" in talks.