North Korea said yesterday it had been holding a tourist from the United States in custody for more than two weeks after he apparently ripped up his visa at immigration and demanded asylum.
The announcement, made in a brief dispatch carried by the North's official KCNA news agency, came as US President Barack Obama wrapped up the first part of a two-day visit to South Korea.
The tourist, identified as "Miller Matthew Todd", 24, had been taken into custody April 10 for "his rash behaviour in the course of going through formalities for entry" into North Korea, KCNA said.
The report said he remained in detention and was under investigation.
North Korea is currently holding another US citizen, Kenneth Bae, described by a North Korean court as a militant Christian evangelist.
Bae, arrested in November 2012, was sentenced to 15 years' hard labour on charges of seeking to topple the government.
According to KCNA, Miller had a tourist visa, but tore it to pieces and shouted that "he would seek asylum" and had come to North Korea "after choosing it as a shelter." There was no immediate reaction from Washington, or Obama's delegation in Seoul.
The announcement appeared to have been timed to coincide with Obama's visit to Seoul, where he warned Pyongyang of sanctions with "more bite" if it went ahead with a fourth nuclear test.
Satellite photos taken just two days ago showed new activity at North Korea's Punggye-ri test site that was "probably related to preparations for a detonation", the US-Korea Institute at Johns Hopkins University said.
Stressing that Washington and Seoul stood "shoulder to shoulder" in their refusal to accept a nuclear North Korea, Obama said Pyongyang's behaviour was even alienating its only major ally, China.
"Threats will get North Korea nothing, other than greater isolation," Obama said at a joint news conference with South Korean President Park Geun-hye. "China is beginning to recognise that North Korea is not just a nuisance but a significant problem for their own security," he added.
Park said a fourth nuclear test by North Korea would "fundamentally shake and alter" the entire security landscape in Northeast Asia. "As a result, the UN would be left with no choice but to slap even stronger punishments on the North," she said.
Both the US and South Korea have repeatedly called on China to use its political and economic influence and exert more pressure on Pyongyang to give up its nuclear weapons programme.
Obama also waded into one of the most contentious issues in Northeast Asia, saying the Japanese wartime system of sex slavery was a "terrible" violation of human rights and its victims need to be heard.
Obama said there needed to be an accounting of the wrongs perpetrated by Japanese Imperial troops before and during the second world war when thousands of women were forced into prostitution.
"This was a terrible, egregious violation of human rights. Those women were violated in ways that even in the midst of war were shocking," he said. "And they deserve to be heard, they deserve to be respected. And there should be an accurate and clear account of what happened."