Seoul: A foreign-funded university in North Korea confirmed on Monday the arrest of a US citizen — the second linked to the school held in two weeks amid tensions on the peninsula.

The detention of Kim Hak-song means that the North is now holding four US nationals, with the two countries at loggerheads over Pyongyang’s nuclear and missile ambitions.

The North detained Kim on Saturday for “hostile acts”, the official KCNA news agency said Sunday, adding he had worked for the Pyongyang University of Science and Technology (PUST).

The school — founded by evangelical Christians from overseas and opened in 2010 — is known to have a number of American faculty members.

PUST confirmed Kim’s arrest, saying he was detained as he was about to leave the country after a visit of several weeks.

“During that visit, Mr Kim was at PUST to do agricultural development work with PUST’s experimental farm,” it said in a statement.

It did not comment on the reason for Kim’s arrest but said it was “not connected in any way with the work of PUST”.

Two weeks ago the North arrested Tony Kim, a US citizen and accounting professor who was lecturing at PUST, accusing him of trying to “overturn” the regime.

Little is known about Kim Hak-song, but his detention brought renewed attention to the school, known to teach many children of the country’s elite.

On its website, PUST says its mission is “to pursue excellence in education, with an international outlook, so that its students are diligent in studies, innovative in research and upright in character, bringing illumination to the Korean people and the world”.

Korean American writer Suki Kim went to PUST undercover as an English teacher in 2011 and later wrote a book about her experiences.

“PUST offers a mutually beneficial arrangement for both North Korea and the evangelicals,” she wrote in an essay published on the Washington Post last month following Tony Kim’s detention.

“The regime gets free education for its youth and a modern facility ... while the evangelicals get a footing in the remote nation,” she said.

Although religious freedom is enshrined in the North Korean constitution, it does not exist in practice and religious activity is severely restricted to officially-recognised groups linked to the government.

The arrest of two Americans in such a short time comes as Pyongyang exchanges hostile rhetoric with the US over its banned missile and nuclear weapons programmes.

Pyongyang has carried out two nuclear tests and dozens of missile launches since the beginning of last year in its quest to build a rocket capable of delivering an atomic warhead to the US mainland.

Washington has suggested military action could be on the table but Trump has softened his message more recently, saying he would be “honoured” to meet Kim.

The four American citizens held in the North also include college student Otto Warmbier and Korean-American pastor Kim Dong-Chul, who received lengthy jail terms for “crimes against the state” and spying, respectively.

The North has occasionally jailed US citizens and released them only after visits by high-profile political figures including former president Bill Clinton.

Clinton in 2009 flew to Pyongyang to negotiate the release of US television journalists Laura Ling and Euna Lee, jailed after wandering across to the North from China.

A year later, another former US president Jimmy Carter visited the North and won the release of American national Aijalon Mahli Gomes, sentenced to eight years of hard labour for illegally crossing into the North from China.