North Korea said it would put two US tourists on trial for committing crimes against the state, dimming any hopes among their families that they would soon be released.
"Their hostile acts were confirmed by evidence and their own testimonies," said the North's official KCNA news agency, referring to Jeffrey Fowle and Matthew Miller who are being held by the isolated country. It gave no details on when they would face court.
It was the latest in a flurry of events in the volatile region as Chinese President Xi Jinping visits South Korea this week, and comes a day after Pyongyang fired two short-range ballistic missiles, defying a UN ban on such tests.
The visit by the head of state of its closest ally to a country with which the North is still technically at war could raise tensions.
Japan has said it will respond to the missile test in co-operation with the United States and South Korea, but that it would not affect talks it is holding with the North this week on the fate of Japanese citizens kidnapped by the reclusive state decades ago.
Jeffrey Fowle, a 56-year-old street repairs worker from Miamisburg, Ohio, was arrested after entering North Korea as a tourist in late April.
A job application uncovered by the Dayton Daily News in Ohio said Mr Fowle described himself as honest, friendly and dependable.
Earlier reports in the paper said Mr Fowle had previously travelled to Sarajevo, Bosnia and had a fascination with the former Soviet Union which led him to look for a Russian bride, whom he later married.
North Korea is one of the most isolated countries in the world, but its economic backwardness and political system is a draw for some Western visitors keen for a glimpse of life behind the last sliver of the Cold War's iron curtain.
"Jeffrey loves to travel and loves the adventure of experiencing different cultures and seeing new places," said a statement from Fowle's family lawyer, released in early June.
"Mrs Fowle and the children miss Jeffrey very much, and are anxious for his return home," the statement said.
Little is known about fellow US citizen Matthew Miller, who was taken into custody by North Korean officials after entering the country the same month whereupon he ripped up his tourist visa and demanded asylum, according to state media.
Mr Miller was traveling alone, said a statement from Uri Tours, the travel agency that took the 24 year-old to North Korea, published on their website.
A spokesman for the New Jersey-based travel agency said Mr Miller was in "good physical condition" and his parents were aware of the situation, but have chosen not to make any statement regarding their son's arrest.
In May, the US State Department issued an advisory urging Americans not to travel to North Korea because of the "risk of arbitrary arrest and detention" even while holding valid visas.