North says imprisoned US citizen Pae Jun-Ho's case will be heard at Supreme Court but fails to give details of charges.
On Saturday, amid soaring tensions between Pyongyang and the West, the KCNA said US citizen Pae Jun-Ho had admitted to the charges and would soon face "judgment".
He has been in prison in the North since November.
"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," the report said. "His crimes were proved by evidence".
Pae was arrested in November as he entered the northeastern port city of Rason, which lies inside a special economic zone near North Korea's border with Russia and China.
will soon be taken to the Supreme Court of the DPRK to face judgment,"
according to the report, which did not say what the charges were based
South Korean media in December identified the detainee as a 44-year-old Korean-American tour operator.
He was travelling with five other tourists and was detained when a computer hard disk was found among the group's belongings, according to the South Korean newspaper Kookmin Ilbo.
Former UN ambassador Bill Richardson delivered a letter regarding Bae to officials during a trip to North Korea in January, although he was unable to meet Bae.
The announcement follows a months-long standoff on the Korean peninsula stoked by the North's nuclear test in February, which prompted the UN Security Council to impose fresh sanctions on the isolated nation.
The move also came hours before US Deputy Secretary of State William Burns was due to meet South Korean Foreign Minister Yun Byung-Se in Seoul for talks on standoff on the Korean peninsula.
Several Americans have been held in North Korea in recent years.
In 2011, a US delegation led by Robert King, the US special envoy for human rights and humanitarian issues, secured the release of Eddie Jun Yong-Su, a California-based businessman, who had been detained for apparent missionary activities.
In 2010, former US president Jimmy Carter won plaudits when he negotiated the release of American national Aijalon Mahli Gomes, sentenced to eight years of hard labour for illegally crossing into the North from China.
On another mercy mission a year earlier in 2009, former president Bill Clinton won the release of US television journalists Laura Ling and Euna Lee, jailed after wandering across the North Korean border with China.
Relations between the two Koreas show little sign of improvement, with Seoul announcing on Friday a complete withdrawal from a jointly run industrial park in the North.