South Korea on Monday rejected North Korea's claim that it had arrested a South Korean citizen on spying charges and demanded that Pyongyang reveal the arrested man's identity. North Korea had on Thursday said that it has arrested a South Korean spy for using "dishonest elements" for a mission seeking to destabilize the country's social system. Media reports had said that the arrested man was a missionary.

A man looks towards North Korea's propaganda village Kaepoong through a pair of binoculars at the Unification Observation Platform, near the demilitarized zone which separates the two Koreas, in Paju, north of Seoul October 16, 2013. South Korean soldiers are everywhere on the south side of the misleadingly named Demilitarised Zone. They guard buildings and man roadblocks to keep the invading hordes at bay. Today the hordes aren't North Korean soldiers. They're tourists. Picture taken on October 16, 2013. REUTERS/Kim Hong-Ji

North's official Korean Central News Agency (KCNA) had reported that security authorities in the North captured the alleged agent of South Korea's intelligence service in Pyongyang, engaged in "plot-breeding activities."

Following reports in the media, the South's National Intelligence Service rejected the claim as groundless. South Korean Unification Ministry on Monday challenged the North to provide further information to support its spying charge against the South.

"Since the North has said it is holding a South Korean in custody, we want his identity to be disclosed," ministry spokesman Kim Eui-Do told reporters.

Following the arrest on Thursday, a spokesperson of the North Korean Ministry of State Security said the detained man confessed to coming into Pyongyang illegally through a third country.

"An initial investigation indicates that he was engaged in anti-DPRK (North Korea) espionage and plot-breeding activities in a third country bordering the DPRK for nearly six years, while disguising himself as a religionist," KCNA said.

The North Korean security agencies had alleged that the detained man entered the North to "rally dishonest elements within the boundary of the DPRK and use them for undermining the stability of the social system in the DPRK."

"This fully proves to what extent the puppet group of conservatives has reached in its anti-DPRK moves," the statement from the North Korean ministry said.

The Chosun Ilbo newspaper in Seoul, meanwhile, citing South Korean activists said the man was a missionary and may have entered the North on a fake passport to meet with churchgoers there.