North Korea says a US soldier who bolted into the North across the heavily armed Korean border last month did so after being disillusioned at the inequality of American society.

It is North Korea’s first official confirmation of the detention of Private 2nd Class Travis King, who entered the North while on a tour of a Korean border village on July 18. He became the first American detained in the North in nearly five years.

The North Korean official news agency, KCNA, on Wednesday said King told investigators that he had decided to enter North Korea because he “harboured ill feeling against inhuman mistreatment and racial discrimination within the US Army”.

It said King also expressed his willingness to seek refuge in North Korea or a third country, saying he “was disillusioned at the unequal American society”.

KCNA is a propaganda arm of North Korea’s dictatorship and often releases statements and articles carefully calibrated to reflect the government’s official line that the United States is an evil adversary.

North Korea said an investigation into King would continue.

Analysts earlier said North Korea might try to use King’s case to wrest concessions from Washington, such as tying his release to the US cutting back its military activities with South Korea.

King’s border crossing came amid heightened animosities on the Korean Peninsula. North Korea has conducted more than 100 weapons tests since the beginning of last year, prompting the US to expand its military drills with South Korea. North Korea views US-South Korean military training as an invasion rehearsal.

King was supposed to be heading to Fort Bliss, Texas, following his release from prison in South Korea on an assault conviction.

According to US officials, King — who chose to serve his time at a labour camp rather than pay the nearly $US4000 ($A6200) fine — has been declared AWOL. The punishment for being away without leave can include confinement in the brig, forfeiture of pay or dishonourable discharge and it is largely based on how long they were away and whether they were apprehended or returned on their own.

The US and North Korea, which fought during the 1950-53 Korean War, are still technically at war since that conflict ended in a truce, not a peace treaty, and have no diplomatic ties. Sweden provided consular services for Americans in past cases, but Swedish diplomatic staff reportedly haven’t returned since North Korea ordered foreigners to leave the country at the start of the COVID-19 pandemic.

North Korea has previously held a number of Americans who were arrested for anti-state, espionage and other charges. But no other Americans were known to be detained since North Korea expelled American Bruce Byron Lowrance in 2018. During the Cold War, a small number of US soldiers who fled to North Korea later appeared in North Korean propaganda films.

US officials have expressed concern about his well-being and said previously that North Korea ignored requests for information about him.