Pyongyang, April 24 (IANS): A US citizen, teaching at the Pyongyang University of Science and Technology (PUST) and detained here on Saturday, has been identified as Kim Sang-duk, also known as Tony Kim, a media report said on Monday

The Korean-American lecturer taught at Pyongyang University of Science and Technology (PUST) for several weeks prior to his arrest, the varsity told the BBC on Sunday.

The investigation into Kim was for matters "not connected in any way" to the university, PUST said.

Kim was arrested just as he was about to leave Pyongyang on Saturday.

North Korean authorities have not yet disclosed the reason for the arrest.

According to South Korea's Yonhap news agency, Kim, who is in his late 50s, was involved in aid programmes and had been in North Korea to discuss relief activities.

He reportedly taught at Yanbian University of Science and Technology in China, which is affiliated to PUST. 

Two other US citizens currently imprisoned by the North Korean regime are Kim Dong-chul, a sexagenarian of South Korean origin captured near the border with China, and Otto Frederick Warmbier, a student who allegedly tried to steal a propaganda poster while visiting as a tourist, Efe news reports.

Both were sentenced this year to 10 and 15 years of forced labour, respectively.