North Korea has detained another U.S. citizen, a university accounting professor in his 50s in the country to teach and discuss relief activities.
South Korea's Yonhap news agency said Tony Kim, who also goes by his Korean name Kim Sang-duk, was arrested Friday at Pyongyang International Airport.
Kim taught accounting at Pyongyang University of Science and Technology for about a month, according to the school's chancellor, Park Chan-mo. Kim had taught at Yanbian University of Science and Technology in China before teaching in North Korea.
The U.S. State Department said "protection of U.S. citizens is one of [its] highest priorities." But the United States has no diplomatic relations with North Korea, and works with the Swedish Embassy in Pyongyang to try to free detained Americans.
"Due to privacy considerations, we have no further comment," the State Department said.
Park said he was told Kim's detention had "nothing to do" with his teaching in North Korea, but did not know further details of his detention.
North Korea did not immediately comment on the arrest.
Kim is the third American held by the regime of North Korean leader Kim Jong Un at a time of tense relations with the United States.
U.S. President Donald Trump has dispatched a naval strike group to the waters off the Korean peninsula as a warning against Pyongyang's continued nuclear weapons development program. The North Korean government, in violation of U.N. decrees, has conducted numerous missile tests and five nuclear tests, with a sixth possible soon.
On Sunday, North Korea said it was ready to sink an aircraft carrier, the USS Carl Vinson, which is the lead ship in the U.S. naval strike group, to demonstrate its military might. U.S. Vice President Mike Pence said Saturday the naval ships would arrive off the Korean peninsula "within days."
North Korea has in the past detained U.S. citizens to use as bargaining chips in its negotiations with Washington.
Last year, Otto Warmbier, a 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, born a South Korean but believed to have U.S. citizenship, is serving 10 years of hard labor for subversion.