File photo of South Korean missionary, identified by the North as Kim Jong Uk, in Pyongyang
File photo of South Korean missionary, identified by the North as Kim Jong Uk, in PyongyangReuters

North Korea has sentenced a South Korean missionary to hard labour for life after a court convicted him of spying and setting up an underground church.

In a report, North Korea's official KCNA news agency said that the South Korean, identified as Kim Jong Uk, had admitted his guilt at a court trial held on Friday.

The news comes just a week after an exchange of fire between forces of the secretive communist North and Western-allied South Korea happened. The Koreas are technically at war since the 1950-53 conflict ended in a truce.

"The accused admitted to all his crimes. He tried to infiltrate into Pyongyang after illegally trespassing on the border for the purpose of setting up underground church and gathering information about the internal affairs of the DPRK (North Korea) while luring its inhabitants into South Korea and spying on the DPRK," KCNA said.

It accused Kim of having illegally entered the North for the purpose of setting up underground church and also getting secret information about Pyongyang's internal affairs.

He was therefore, sentenced to "life (at) hard labor," it said.

Meanwhile, South Korea's National Intelligence Service has insisted that Kim, who was arrested by the North in October, is not its agent, South Korean Yonhap News Agency reports.

The accused is known to have worked as a missionary in the Chinese border town of Dangung, the news agency said. His age and other personal details, however, have not been made public.

Pyongyang, meanwhile, has rejected calls from Seoul for his release and for his family to visit him, Reuters reports.

The news comes amid increased tension over the maritime border where Seoul, earlier this month, accused the North of firing two artillery rounds near a South Korean navy patrol ship. South replied with several rounds of firing.

North Korea - which continues to shock political analysts and public throughout the world with its ancient-style belligerent language and rhetoric - has denied the firing.

In a similar case, North Korea last year sentenced American citizen and a missionary, Kenneth Bae to 15 years of hard labor on charges of trying to use religion to overthrow its power strata.

The isolated and reclusive communist nation continues to be mysterious since no one really knows what exactly happens in the nation, although widespread instances of human rights violation, arbitrary killings and execution of people for petty reasons and a large-scale population struggling in malnourishment and poverty, have been frequently reported.