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North Korea has acknowledged that it is holding an American national, the US state department has said.

The captive's identity has not been confirmed as consular access has not been granted, AP news agency reports.

The disclosure comes amid concern for Merrill Newman, 85, who was reportedly detained weeks ago in North Korea.

Mr Newman's family have appealed to Pyongyang to free him, saying there has been "some dreadful misunderstanding" and that he may need medication.

North Korea's acknowledgement came via Swedish officials, who oversee consular issues for the US as it lacks diplomatic ties with North Korea.

The Swedish embassy in Pyongyang had been requesting access to the American on a daily basis, a state department spokesman said.

Mr Merrill's wife Lee said the family had had "no word on the state of his health, whether or not the medications sent to him through the Swedish Embassy in North Korea have been delivered or why he was detained".

"The family feels there has been some dreadful misunderstanding leading to his detention and asks that the DPRK [Democratic People's Republic of Korea] work to settle this issue quickly and to return this 85-year-old grandfather to his anxious, concerned family," she said in a statement.

The couple's son, Jeffrey Newman, said earlier that Mr Merrill, a Korean War veteran, was taken off a plane by uniformed officers on 26 October at the end of a trip to North Korea.

He was visiting the country with a friend, on a guided tour arranged with a travel agent "approved by the North Korean government for travel of foreigners", Jeffrey Newman said.

US officials have not specifically confirmed the case, but have called on North Korea to "resolve the issue".

Merrill Newman appeared to have discussed his experience in the Korean War with North Korean officials the day before his detention, his son added.

Another veteran, also named Merrill Newman, was awarded a Silver Star medal for his efforts during the Korean War. In an interview with Reuters news agency, he said that he thought it was possible there had been "a case of mistaken identity".

The state department revised its travel guidance for North Korea this week, saying: "US citizens crossing into North Korea, even accidentally, have been subject to arbitrary arrest and long-term detention."

Another US citizen, Kenneth Bae, has been detained since November 2012.

US troops backed South Korea in the 1950-53 Korean War, which killed at least two million people.