A US citizen entered North Korean territory during a tourist visit to the heavily guarded border with South Korea and is believed to have been detained, the UN command for that sector said Tuesday.

“A citizen of the United States has crossed the military demarcation line without authorization” with the Democratic People’s Republic of Korea (DPRK), while visiting the Common Security Area, the sector controlled by the United Nations, the UN command post said. referring to the border between North Korea and South Korea.

“We believe he is currently being held in the DPRK, and we are working with our colleagues in the Korean People’s Army to resolve the incident,” the United Nations command post added, referring to the North Korean military.

Since the 1950-1953 Korean War ended with an armistice rather than a peace treaty, the two countries remain technically in conflict, their heavily guarded border consisting of a demilitarized zone at the 38th parallel.

Soldiers from both states work face-to-face in the Common Security Area, north of Seoul, under UN command surveillance.

The site is also a popular tourist destination, with hundreds of visitors arriving from the South Korean side every day.

In 2019, then-US President Donald Trump met with North Korean leader Kim Jong-un in the border town of Panmunjom, and was even on North Korean territory when he crossed the demarcation line.

According to the South Korean television channel SBS, the person who crossed the border is a US soldier. South Korea’s defense ministry declined to comment to AFP.

A witness, who claimed to have participated in the same field trip, told CBS News that the group had been visiting one of the nearby buildings when “this man let out a loud ‘ha ha ha’ and started running between the two buildings.”

“At first I thought it was a bad joke but when it didn’t come back I realized it wasn’t a joke and then everyone reacted and it went crazy,” he explained.

US nuclear submarine in South Korean port

North Korea closed its borders at the start of the Covid-19 pandemic, in 2020, and has not reopened them yet. It also significantly reduced security in his part of the demilitarized zone.

Under the ceasefire protocol, neither U.S. nor South Korean personnel are allowed to cross the border to pick up the U.S. citizen.

The incident came at a time when relations between the two Koreas are at a minimum. Diplomatic action has stalled and North Korean leader Kim Jong-un has called for the development of his country’s weapons, including tactical nuclear weapons.

South Korea and the United States have intensified defense cooperation by organizing joint military exercises; a number of exercises that will be done again next month.

Both allied countries held the first meeting of a Nuclear Consultative Group this Tuesday in Seoul aimed at improving nuclear coordination between the two allied countries and strengthening military preparation for North Korea.

In addition, they announced that a US nuclear submarine had made a stopover in the South Korean city of Busan for the first time since 1981.

This could provoke a strong reaction from North Korea.

Kim Yo Yong, Kim Jong Un’s powerful sister, said on Monday that the submarine deployment will only “move Pyongyang further” from any talks. Last week he already warned the United States in case another US plane flies over the waters of its EEZ.