An 85-year-old US war veteran has been detained in North Korea where he was on holiday.

Merrill Newman, from Palo Alto, California, was on a plane ready to take off from Pyongyang at the end of a nine-day trip to the secretive nation when security forces boarded the aircraft and asked him to follow them.

"My dad got off, walked out with the stewardess, and that's the last he was seen," Newman's son Jeffrey said.

Newman was arrested at the end of October but the family initially decided to keep a low profile, not reporting it to the media.

Jeffrey Newman said he has been in regular contact with the US State Department, which however has refused to confirm the arrest, the reasons for which remain unclear.

"We don't know what this misunderstanding is all about," he said. "All we want as a family is to have my father, my kids' grandfather, returned to California so he can be with his family for Thanksgiving."

Family and friends suggested the arrest might have been linked to Newman's military service during the Korean War.

The 85-year-old was travelling with Bob Hamrdla, a friend who was living in the same Californian retirement community and was allowed to return home by North Korean authorities.

Hamrdla reportedly said that the day before the arrest Newman was briefly quizzed about his three years of service as an infantry officer in Korea, during the 1950-53 conflict between US-led United Nations forces and North Korea and China.

Newman's son told CNN his father was a "bit bothered" by the incident but didn't believe the conversation would land him in trouble.

At least six Americans have been detained by Pyongyang since 2009 amid the tense standoff between the two countries.

Newman suffers from a heart condition and his son said he has delivered medication to the Swedish ambassador who is acting as a mediator since the US has no diplomatic presence in North Korea.

Pyongyang has neither publicly commented on nor confirmed the arrest.