An American soldier is detained by North Korea after crossing its heavily armed border

SEOUL, South Korea (AP) — An American soldier crossed the heavily armed border from South Korea into North Korea, U.S. officials said Tuesday. He went “willfully and without authorization,” the U.S. military said, becoming the first American detained in the North in nearly five years at a time of heightened tensions over its nuclear program.

There were no immediate details about why or how the soldier crossed the border or whether he was on duty. The five U.S. officials spoke on the condition of anonymity to discuss the matter ahead of a public announcement.

The American-led U.N. Command overseeing the area tweeted earlier Tuesday that the detained soldier was on a tour of the Korean border village of Panmunjom. The soldier purposefully separated himself and ran away from the rest of the group, according to a U.S. official who was not authorized to comment. The official added that it’s “not normal” for active duty service members to go on such tours.

The U.S. military in South Korea also said in a statement that he “willfully and without authorization” crossed the military demarcation line into North Korea.

It said that he is believed to be in North Korean custody and that the U.N. Command is working with its North Korean counterparts to resolve the incident. North Korea’s state media didn’t immediately report on the border crossing.

Cases of Americans or South Koreans defecting to North Korea are rare, though more than 30,000 North Koreans have fled to South Korea to avoid political oppression and economic difficulties since the end of the 1950-53 Korean War.

Panmunjom, located inside the 154-mile-long Demilitarized Zone, has been jointly overseen by the U.N. Command and North Korea since its creation at the close of the Korean War. Bloodshed and gunfire have occasionally occurred there, but it has also been a venue for numerous talks and is a popular tourist spot.

Known for its blue huts straddling concrete slabs that form the demarcation line, Panmunjom draws visitors from both sides who want to see the Cold War’s last frontier. No civilians live at Panmunjom. In the past, North and South Korean soldiers faced off within yards of each other.

Panmunjom also is where the armistice that ended the Korean War was signed. That armistice has yet to be replaced with a peace treaty, leaving the Korean Peninsula technically in a state of war. The United States still stations about 28,000 troops in South Korea.

There have been a small number of U.S. soldiers who went to North Korea during the Cold War, including Charles Jenkins, who deserted his army post in South Korea in 1965 and fled across the DMZ. He appeared in North Korean propaganda films and married a Japanese nursing student who had been abducted from Japan by North Korean agents. He died in Japan in 2017.

But in recent years, some American civilians have been arrested in North Korea after allegedly entering the country from China. They were later convicted of espionage, subversion and other anti-state acts but were often released after the U.S. sent high-profile missions to secure their freedom.

In May 2018, North Korea released three American detainees — Kim Dong Chul, Tony Kim and Kim Hak Song — who returned to the United States on a plane with then-Secretary of State Mike Pompeo during a short-lived period of warm relations between the longtime adversaries. Later in 2018, North Korea said it expelled American Bruce Byron Lowrance. Since his ouster, there have been no reports of other Americans detained in North Korea before Tuesday’s incident.

Their freedoms were a striking contrast to the fate of Otto Warmbier, an American university student who died in 2017 just days after he was released by North Korea in a coma after 17 months in captivity. Warmbier and other previous American detainees in North Korea were imprisoned over a variety of alleged crimes, including subversion, anti-state activities and spying.

The United States, South Korea and others have accused North Korea of using foreign detainees to wrest diplomatic concessions. Some foreigners have said after their release that their declarations of guilt were coerced while in North Korean custody.