U.S. citizen detained at North Korean airport

April 23 (UPI) -- North Korean authorities detained a Korean-American man at Pyongyang International Airport, a Swedish diplomat said.

The man has only been identified by his surname, Kim, and the reasons for his detention are unknown.

"He was prevented from getting on the flight out of Pyongyang," Martina Aberg, deputy chief of mission at the Embassy of Sweden in North Korea, told CNN. "We don't comment further than this."

For the past several months, the detained U.S. citizen, who is in his late 50s, has been involved in aid programs in North Korea. He was previously employed as a professor at Yanbian University in China.

The arrest, which occurred on Saturday, comes amid heightened tensions in the region. Both the United States and South Korea have expressed displeasure at North Korea's missile tests and continued efforts to develop nuclear weapons.

Earlier this month, Vice President Mike Pence called a failed North Korean missile test a "provocation." National security adviser Lt. Gen. H.R. McMaster said the problem of North Korea's military ambition is "coming to a head."

U.S. and Japanese forces are conducting joint military exercises in the nearby Philippine Sea.

Kim is the third American arrested in North Korea. U.S. citizens Otto Warmbier and Kim Dong-chul are serving time in North Korean prisons for "subversive acts."

The United States has in the past accused North Korea's government of detaining U.S. citizens for use as political pawns.

"[North Korea] seems to be intending to use professor Kim as leverage in negotiations," Ahn Chan-il, president of the World North Korea Research Center in Seoul, told South Korean news agency Yonhap.