HONG KONG — North Korea said Saturday that a man it identified as a South Korean student at New York University had been arrested and charged with illegally entering the country.

The North’s official Korean Central News Agency said the student, Joo Won-moon, 21, from New Jersey, was detained on April 22 after crossing the Yalu River from Dandong, China. The river forms part of the North’s border with China.

Mr. Joo, who is said to hold permanent resident status in the United States, admitted violating North Korean law, said the news agency, which added that an investigation was continuing. The South Korean government said it could not immediately confirm the North Korean news report.