U.S. citizen detained in North Korea

A former Korean-American professor was arrested in North Korea last week, becoming the third U.S. citizen to be detained by Pyongyang of late.

Citing sources South Korea's Yonhap news agency reported on Sunday that the U.S. citizen, identified only by his surname Kim, was arrested by North Korean authorities on Friday at Pyongyang International Airport on his way out of the country.

The former professor at the Yanbian University of Science and Technology, who is in his late 50s, has been engaged in aid and relief programs to North Korea.

He reportedly was in the North for about a month to discuss relief activities. The reason for his arrest was not clear.

Two other U.S. citizens - college student Otto Warmbier and Korean-American pastor Kim Dong-chul - are also currently detained in North Korea after being sentenced to long prison terms for 'subversive acts against the country'.

Ahn Chan-il, director of the World North Korea Research Center in Seoul, said that the North "seems to be intending to use professor Kim as leverage in negotiations" amid the current bad relations between the two countries.

Since 2009, over 10 U.S. citizens have been detained in North Korea on charges of anti-state and other unspecified crimes.

Tensions between the United States and the North have risen sharply in recent weeks as a series of North Korean missile tests have prompted dire warnings from President Donald Trump's administration.