North Korea has detained another American who worked at a private university in Pyongyang, taking to four the number of U.S. citizens being held by Kim Jong Un’s regime.

Kim Hak-song, who worked for the Pyongyang University of Science and Technology, was detained Saturday, North Korea’s state news agency said.

Kim was arrested on suspicion of “hostile acts” against North Korea, the official Korean Central News Agency said. “A relevant institution is now conducting a detailed investigation into his crimes,” it said.

No other details about him were available.

The State Department said Sunday that it was “aware of reports that a U.S. citizen was detained in North Korea.”

“The security of U.S. citizens is one of the department’s highest priorities,” a spokeswoman said, adding that the department was working with the Swedish Embassy, which represents the United States in North Korea.

“Due to privacy considerations, we have no further comment,” she said.

Two weeks ago, North Korea detained another U.S. national, Kim Sang-dok or Tony Kim, as he waited to board a flight at Pyongyang airport. He had been teaching a class in international finance and management at the same university, known as PUST.

PUST is the only private educational institution in North Korea. It is run by a Korean American professor and funded largely by Christian groups. It began offering classes in English to the North Korean elite in 2010.

PUST has more than 60 foreign faculty members, including from the United States, Canada, Britain and China, its website says.

“The mission of PUST 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,” it says.

Suki Kim, a Korean American author who taught at PUST for six months and wrote a book about it, described the faculty members holding private prayer meetings and Bible study sessions.

All religion is banned in North Korea, a totalitarian state that requires all its citizens to worship the three generations of the Kim family who have run the country through a personality cult since the end of World War II.

However, PUST appears to have been tolerated as long as its Christian activities were conducted behind closed doors and the faculty did not try to proselytize to the North Korean students.

Two other U.S. citizens also are being held in North Korea.

One is former Virginia resident Kim Dong-chul, who had been living in the Chinese city of Yanji, near the border with North Korea, and working in a special economic zone in the North as head of a trade and hotel services company.

He is in his early 60s and was born in South Korea but became a U.S. citizen in 1987; he was sentenced to 10 years in prison in April 2016 on charges of spying.

The other is Otto Warmbier, a University of Virginia student who was detained for allegedly trying to steal a propaganda sign from a Pyongyang hotel on New Year’s Day last year while on a group tour.

Warmbier was convicted of subversion in March and sentenced to 15 years of hard labor. That was the last time that he was seen and that Swedish diplomats were allowed to meet with him.

The State Department advises Americans against traveling to North Korea, warning of “the serious risk of arrest and long-term detention under North Korea’s system of law enforcement.”

The detentions come at a time of heightened tensions between Washington and Pyongyang.

President Trump has been vacillating between calling Kim Jong Un a “smart cookie” and threatening military action against North Korea, while the Kim regime has been warning of a nuclear attack in the face of any U.S. threat.

In the latest development, North Korea accused the United States and South Korean intelligence agencies on Friday of plotting to kill Kim Jong Un using “biochemical substances.”

North Korea’s Foreign Ministry called the agencies “hotbed of evils in the world” and said in a statement that they had “hatched a vicious plot to hurt the supreme leadership.”

The statement said that a citizen, identified only as Kim, had been paid $290,000 for himself and his “terrorist accomplices” as part of the alleged plot. He was supposed to target the “supreme leadership” at a public event or military parade, using “bomb terrorism” that involved “biochemical substances including radioactive substance and nano-poisonous substance,” it said.

Kim is the most common surname on the Korean Peninsula, used by about a quarter of all Koreans.

Read more:

Worried about North Korea? Spare a thought for Otto Warmbier’s family.

North Korea accuses CIA and South Korea of plotting to assassinate Kim Jong Un

Today’s coverage from Post correspondents around the world

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