An 85-year-old American veteran of the Korean War has been detained for almost a month in North Korea, his family has said.
Merrill Newman, of Palo Alto, California, was pulled off a plane on October 26 as he was about to leave the country.
His son, Jeffrey Newman, said an officer boarded the plane, asked to see his father's passport and then asked a stewardess to make him leave the plane.
"My dad got off, walked out with the stewardess, and that's the last he was seen," he said, speaking from California.
Jeffrey Newman also said that the day before, his father and his tour guide spoke with North Korean authorities at a meeting in which his military service in Korea was discussed.
"We think that the conversation was difficult at times," he said, adding that he did not know the details.
Mr Newman was travelling with friend Bob Hamrdla, who was allowed to return and said in a statement that: "There has to be a terrible misunderstanding.
"I hope that the North Koreans will see this as a humanitarian matter and allow him to return to his family as soon as possible."
Pyongyang has also been holding Kenneth Bae, a Korean-American Christian missionary, since November 2012.
Mr Bae faced several charges that all implied he had been attempting to help topple Kim Jong-Un's regime and was sentenced to 15 years of hard labour.
The US special representative for North Korea policy, Glyn Davies, urged North Korea to "resolve the issues" of Americans detained in North Korea, including Mr Bae and Mr Newman.
Mr Newman is believed to have entered the reclusive nation with a valid visa for sightseeing last month. He was on a 10-day trip, reports said.
The younger Mr Newman said his family has been in contact with the State Department and had arranged for heart medication needed by his father to be delivered to the North Koreans through Swedish diplomats.
The US has no diplomatic relations with North Korea.
The elder Mr Newman served as a US infantry officer in the Korean War and later worked as a manufacturing and finance executive before retiring in 1984, according to a biography of him in a February 2012 newsletter from Channing House, the Palo Alto retirement home where he now lives.
A State Department advisory to American travellers warns that "US citizens crossing into North Korea, even accidentally, have been subject to arbitrary arrest and long-term detention".
North Korea says the detained man had broken the law, according to Japan's new agency Kyodo.