Tony Kim, who also goes by the Korean name of Kim Sang-duc, was arrested on Saturday at Pyongyang's Sunan International Airport as he was preparing to depart from North Korea, following a month-long working visit.
The professor, in his mid-50s, formerly taught accounting at China's Yanbian University of Science and Technology, just north of the North Korea/China border. While in North Korea, Kim had been involved in an undisclosed form of relief activity, according to Stripes.com. Pyongyang has made no official statement regarding the reason for the arrest.
According to Ahn Chan-il, the director of the World North Korea Research Center in Seoul, South Korea, Pyongyang "seems to be intending to use professor Kim as leverage in negotiations."
North and South Korea are currently at rigid diplomatic odds with each other. Seoul's National Intelligence Service said in a statement that it "was not aware" of the professor's arrest.
The Swedish embassy in Pyongyang, acting on behalf of the United States in diplomatic relations with North Korea, stated that it was aware of the arrest but could not provide further details.
Park Chan-mo, chancellor of the Pyongyang University of Science and Technology, stated that Kim had taught at Yanbian University in China prior to joining Park's team. Park assured Yonhap News in a statement that he had been told that Kim's work as a professor at the university had "nothing to do" with his arrest.
As of Sunday night, there had been no official announcement from Pyongyang regarding the arrest and detention of the US citizen.
The arrest coincides with a period of extremely high tensions in the region, due primarily to Pyongyang's continued test-firing of ballistic missiles and underground detonations of nuclear weapons.
Washington and Pyongyang have traded increasingly strident military threats with each other recently, resulting in calls from US regional allies and China asking that both nations calm down.
Two other Americans, including 21-year-old University of Virginia student Otto Warmbier, who was sentenced to 15 years of hard labor after trying to steal a propaganda banner as souvenir, and Christian priest Kim Dong Chul, who is serving ten years for espionage, have contributed to the increasing strain in relations between Pyongyang and Washington.
At least ten US citizens have been arrested and sentenced in North Korea since 2009, according to Yonhap. Many believe that the Americans are held primarily as diplomatic bargaining chips by Pyongyang.