SEOUL (AFP) - North Korea said Saturday that it would put a US citizen on trial for trying to overthrow the communist regime, in the face of soaring tensions between Pyongyang and the West.

The North's official Korean Central News Agency (KCNA) said Pae Jun Ho had admitted to the charges and would soon face "judgment".

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.

Mr Pae, who is believed to be a Korean-American tour operator, was arrested in November as he entered the north-eastern port city of Rason.

KCNA said a "preliminary inquiry" had been completed.

"He admitted that he committed crimes aimed to topple the DPRK (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 judgment," according to the report, which did not say what the charges were based on.

Seoul-based activist Do Hee Yoon told AFP that he suspected Mr Pae was arrested because he had taken photographs of emaciated children in North Korea as part of efforts to appeal for more outside aid for them.

The North's announcement came hours before US Deputy Secretary of State William Burns met South Korean Foreign Minister Yun Byung Se for talks in Seoul. The US diplomat did not publicly comment on the trial.

In Washington, the State Department said it was "aware of reports that a US citizen will face trial in North Korea" and was working in "close coordination" with representatives from the Swedish embassy in Pyongyang.

"Welfare of US citizens overseas is a critical priority of the Department of State," spokesman Jen Psaki said, adding: "The Embassy of Sweden in Pyongyang visited the US citizen on Friday, April 26." The statement, which said the department had no additional information to share at this time, did not name Pae.

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 have worsened markedly in recent months, with Seoul announcing on Friday a complete withdrawal from a jointly run industrial park in the North after Pyongyang rejected its ultimatum to join formal negotiations on restarting the stalled operations.

The move plunged into doubt the future of the Kaesong complex - once a rare symbol of cooperation across the world's most heavily militarised border, and a crucial source of hard currency for Kim Jong Un's isolated regime.

A total of 126 workers from the site returned to South Korea on Saturday in dozens of vehicles loaded with assembled goods and other materials.

The roughly 50 people remaining - mostly government employees who manage the site as well as telecom and electrical engineers - are expected to be pulled out on Monday.

South Korean companies with factories in Kaesong have expressed shock at the abrupt withdrawal.

"We're dismayed at the sudden government decision to pull out of Kaesong.

We're concerned this would eventually result in its closure," a representative of the 123 South Korean firms with interests there told reporters.

Established in 2004, the complex lies 10km inside the North, which remains technically at war with the South after the 1950-53 Korean War was concluded with a ceasefire rather than a peace treaty.