SEOUL/WASHINGTON - South Korea on Monday urged Pyongyang to release four of its citizens being held by the North, including two men who told CNN they spied for the South, and a 21-year-old New York University student.
Two men arrested by North Korea in March said in interviews with CNN that they spied for South Korea's intelligence agency, but the cable television news network said it could not verify their accounts.
North Korea said Kim Kuk Gi and Choe Chun Gil were South Korean nationals working as spies for Seoul's National Intelligence Service from the Chinese border city of Dandong.
North Korean state media accused one of them of running an "underground church" and spreading foreign information on USB sticks and SD memory cards in the country.
South Korea has called the allegations "groundless".
On Saturday, Pyongyang said it had arrested a South Korean man with a US green card who was a student at New York University. Joo Won-moon, 21, was detained on April 22 crossing from the Chinese side of the Yalu River, according to North Korea's KCNA news agency.
"As North Korea repeatedly commits anti-humanitarian acts, it will draw stronger criticism from South Koreans and the international community," South Korean Unification Ministry spokesman Lim Byeong-cheol told reporters on Monday.
In late March, the South sent a message to the isolated North proposing a meeting to discuss the detentions of Choe and Kim but the North declined to accept it, Lim said. He said South Korea had been seeking diplomatic help from countries that have embassies in both countries.
On Sunday, CNN said that North Korea had made Choe and Kim available for separate interviews, with official minders present.
The network said it could not independently verify the accounts, which it said were similar to each other and to a North Korean state media report in March about their arrests.
Choe told CNN he had been a businessman and worked as a spy for three years. He said he was arrested while trying to obtain boxes of materials from North Korea that were related to military operations, CNN reported.
Kim said he was a missionary and worked as a spy for nine years. He told CNN that South Korea's National Intelligence Service wanted itineraries of foreign leaders visiting North Korea and other information.
The two are awaiting trial.
North Korea has arrested others it believed were spies in recent years.
New York University said Joo was a student at its Stern School of Business but not taking classes this semester. The school said it was unaware of his travels.
"NYU has been in touch with the US State Department about this matter, as well as the South Korean embassy," school spokesman John Beckman said. The school added it had also contacted his family to express its support.
North Korea is also holding a South Korean missionary who was sentenced to life with hard labour last year for espionage and setting up an underground church.
Last year, Pyongyang released three detained Americans including Kenneth Bae, a Korean-American missionary who had been held for two years.