North Korea is to put a US citizen on trial for conspiracy to overthrow the regime after he was arrested entering the country as a tour guide to a group of tourists.
Pae Jun-ho, 44, known in the US as Kenneth Bae, is said by authorities in Pyongyang to have "admitted that he committed crimes aimed to topple the Democratic People's Republic of Korea with hostility toward it", according to North Korea's state news agency KCNA.
Pae was arrested in November as he accompanied five Europeans into Rason, a special economic zone in the north-east of the country which is open to foreign companies.
The exact charges he faces remains unclear, along with the date when a verdict was expected. Nor was it clear what punishment he faced, though officials said the penalties would be very serious, and included a possible death sentence.
Tensions remain high between Pyongyang and Washington following the North's third nuclear test in February.
"The preliminary inquiry into crimes committed by American citizen Pae Jun-ho closed," the KCNA said.
"In the process of investigation he admitted that he committed crimes aimed to topple the Democratic People's Republic of Korea with hostility toward it.
"His crimes were proved by evidence. He will soon be taken to the Supreme Court of the DPRK to face judgement," the agency added.
US authorities made no comments on the statement.
In January, Bill Richardson, the governor of New Mexico, and Eric Schmidt, the chief executive of Google, travelled to North Korea to negotiate Pae's release, but were denied access to him.
Pae, who is of Korean descent, is the sixth American detained in North Korea since 2009. Several US citizens, including journalists and Christians accused of proselytism, have been released in recent years after intervention by senior US statesmen.
Former Presidents Bill Clinton and Jimmy Carter have both been involved in mediation efforts to secure the release of detainees. Clinton negotiated the release in 2009 of US journalists Laura Ling and Euna Lee, after they were found guilty of entering North Korea illegally.
"For North Korea, Pae is a bargaining chip in dealing with the US," said Koh Yu-hwan, a professor of North Korean studies at Dongguk University in Seoul. "The North will use him in a way that helps bring the US to talks when the mood slowly turns toward dialogue."
Pae's father is understood to live in South Korea while his mother lives in the US. His family has declined to comment for fear of aggravating the situation.
Pae, who previously lived in China, ran a travel agency called Nation Tours. He had visited North Korea several times, according to Do Hee-youn, head of the Citizens' Coalition for the Human Rights of North Korean Refugees, based in Seoul.
He said Pae may have been arrested for taking photographs of orphans begging for food in the markets of Rason.
"The most plausible scenario I can think of is that he took some pictures of the orphans, and the North Korean authorities considered that an act of anti-North Korean propaganda," he said.
However, no foreign visitor to North Korea has yet been arrested for taking photographs.
South Korean media reported that North Korean officials recovered a hard disk from Pae containing sensitive information.
The US special envoy for North Korean human rights issues, Robert King, said Pyongyang had so far made no request for an envoy to negotiate Pae's release.
Pae is believed to be a Christian. His Facebook page contains links to an organisation named the Joseph Connection, based in Ohio, which describes itself as "a Christ-centred, humanitarian outreach to the Least of the Least world-wide" and states that it "organizes short-term trips into closed or restricted countries to touch the average person".
Religious evangelising is treated as a serious crime in North Korea, and Christian missionaries have been severely punished.
In a further sign of rising tensions on the peninsula, South Korea began withdrawing workers from the Kaesong joint industrial complex, formerly a symbol of reconciliation close to the North-South border.