The US was on Wednesday scrambling to establish the fate of Travis T King, who was on a civilian tour of the village of Panmunjom between the two Koreas, when he reportedly bolted into North Korea on Tuesday.
“We believe that he is in (North Korean) custody and so we’re closely monitoring and investigating the situation,” US Defence Secretary Lloyd Austin told a briefing, while North Korea remained silent.
Mr King’s mother, Claudine Gates, told ABC News she was shocked when she was informed by the US Army on Tuesday about what had happened.
“I can’t see Travis doing anything like that,” said Ms Gates, of Racine, Wisconsin, said.
She said she last heard from her son “a few days ago,” when he told her he would return soon to Fort Bliss, an Army post in the southern US.
She added she just wants “him to come home.”
Mr King, who joined the US Army in 2021, was understood to be facing disciplinary action, and to have been on his way back to the US when he decided to cross the border.
US officials were stumped as to why the soldier fled to the North, and outlined a puzzling series of events.
Mr King had finished serving time in detention in South Korea for an unspecified infraction and was transported by the US military to the airport to return to his home unit in the United States, two US officials said.
He had already passed alone through security to his gate when he decided to flee, one official said.
Civilian tours of the demilitarised zone are advertised at the airport and Mr King appeared to have decided to join one, the official added.
US Defence Secretary Mr Lloyd said Mr King was on an orientation tour of Joint Security Area (JSA) on the border between the two Koreas on Tuesday, when he crossed the line marking the Military Demarcation Line border and went into North Korea “wilfully and without authorisation”.
The heavily armed border has separated the two Koreas since fighting in the Korean War ended in 1953 in an armistice.
North Korea’s state media has made no mention of the incident.
The crossing comes at a time of renewed tension on the Korean peninsula, with the arrival of a US nuclear-armed ballistic missile submarine, and the launch early on Wednesday morning of two ballistic missiles into the sea by North Korea.
North Korea has been testing increasingly powerful missiles capable of carrying nuclear warheads, including a new solid-fuel intercontinental ballistic missile launched last week.
Colonel Isaac Taylor, a spokesperson for US Forces Korea, said the military was “working with our KPA counterparts to resolve this incident,” referring to North Korea’s People’s Army.
Two US officials, who spoke on condition of anonymity, said the soldier had been due to face disciplinary action by the US military. But he was not in custody at the time he decided to flee, one of them said.
South Korea’s Unification Ministry, which handles ties with the North, said all tours to Panmunjom have been cancelled indefinitely on the request of the UN Command which oversees security for the area.
It was unclear how long North Korean authorities would hold the soldier but analysts said the incident could be valuable propaganda for the isolated country.
Before dawn on Wednesday, North Korea fired two ballistic missiles from an area near its capital, Pyongyang, each flying 550 km and 600 km before plunging into the sea off its east coast.
The launch comes hours after the South Korea and the United States held the first round of talks on Tuesday on upgrading coordination in the event of a nuclear war with North Korea.
The United States has pledged to deploy more strategic assets such as aircraft carriers, submarines and long-range bombers to South Korea, drawing an angry response from Pyongyang which vowed to escalate its own military response.