Washington has urged North Korea to free on “humanitarian grounds” a US citizen who Pyongyang claims admitted to plotting against the regime.

Having no diplomatic relations with the North, the United States coordinated with Sweden in seeking the release of Pae Jun-Ho, also known as Kenneth Bae, after Pyongyang said the Korean-American tourist will “face judgement” soon on charges of trying to overthrow the regime.

“The welfare of US citizens is a critical and top priority for this department. We call on the DPRK to release Kenneth Bae immediately on humanitarian grounds,” deputy acting State Department spokesman Patrick Ventrell said.

US officials insisted Bae, who was arrested in November last year in the northeastern port city of Rason, had entered North Korea on a valid visa.

Washington also raised concerns that Bae could be used as a tool in some sort of “political bargain” amid escalating tensions between the US and North Korea since Pyongyang carried out its third nuclear test in February.

The official Korean Central News Agency said Saturday that a “preliminary inquiry” had been completed.

“He admitted that the committed crimes aimed to topple the DPRK with hostility toward it,” KCNA reported. “His crimes were proved by evidence”. The charge carries a maximum punishment of death penalty.

Evidence referred to by Pyongyang may be Bae’s photographs of orphans begging in Rason which the regime considers an act of anti-North Korean propaganda, says Do Hee-yuon, head of the Citizens’ Coalition for the Human Rights of North Korean Refugees.