North Korea says it has arrested an American national for committing a "hostile act" against the regime.

The North's official Korean Central News Agency said Friday that authorities were investigating the University of Virginia student identified as Warmbier Otto Frederick.

The agency claimed he entered the North posing "as a tourist with a plot to undermine a unity among the North Koreans." It said the student has links to the U.S. government.

It also said the student was caught taking part in anti-North Korea activity but did not elaborate.