A detained South Korean missionary has appeared before media in North Korea to read from a statement publicly apologising for "anti-state crimes".
Baptist Kim Jong-uk, 50, said he was arrested after entering via China with religious materials in October.
Religious activity is restricted in the North, with missionaries arrested on multiple occasions in the past.
Foreign nationals arrested in North Korea sometimes make public confessions which they later say were under duress.
Merrill Newman, an 85-year-old US national, was briefly held last year. He was freed after confessing to committing crimes during the Korean War - a statement he said was given under duress.
'Destroying the system'
In his first public appearance since his arrest, Mr Kim said he wanted to let his family know he was in good health.
He said he acted "under directions" from South Korea's National Intelligence Services (NIS), setting up an underground church in Dandong, China, to collect information on life in North Korea to send back.
"I was thinking of turning North Korea into a religious country, and destroying its present government and political system," he also told the news conference.
One report said Mr Kim had been working in Dandong for seven years helping North Korean refugees.
Mr Kim said he was unsure of his punishment and asked that he be released.
The North's state media in November said it had arrested an unnamed South Korean "spy", a charge which South Korea's intelligence agency denied.
On Thursday, South Korea's Unification Ministry urged North Korea to release and repatriate Mr Kim.
"It's hard to understand how our citizen, involved in purely religious activities, was rated an anti-state criminal," spokesman Kim Eui-do said.
'We know nothing'
Meanwhile, Australia's foreign ministry said it had not received any information about John Short, 75, a missionary who was arrested at his hotel in Pyongyang last week.
Mr Short, an Australian based in Hong Kong who entered Pyongyang on a group tour, was detained after apparently leaving Christian pamphlets at a tourist site.
"We do not know anything about the conditions in which he's being held," Justin Brown, head of the consular section, told a parliamentary hearing in Australia.
Australia does not have diplomatic representation in Pyongyang and is being represented by the Swedish embassy.
In November 2012, North Korea also arrested Korean-American missionary Kenneth Bae. He is currently serving 15 years of hard labour after being convicted of trying to overthrow the government.
Efforts from Washington to secure Mr Bae's release have so far been unsuccessful.