WASHINGTON (Reuters) - Two men arrested by North Korea in March said in interviews with CNN that they spied for South Korea's intelligence agency, the cable television news network reported on Sunday.

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 accusations "groundless."

On Sunday, CNN reported North Korea made the two men 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.

North Korea has arrested others it believed were spies in recent years.

On Saturday, it said it arrested a South Korean man with a U.S. 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.

The 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 U.S. 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.