The family of an American Christian missionary imprisoned in North Korea last year says he is seriously ill and has been moved from a prison work camp to a hospital within the past two weeks.
Kenneth Bae was sentenced in May to 15 years' hard labour after the reclusive nation's Supreme Court convicted him of state subversion. The court said Bae, 45, had used his tourism business to form groups to overthrow the government.
The US government has called for Bae's immediate release on "humanitarian grounds".
Bae has chronic diabetes, an enlarged heart and suffers from back and leg pain, according to his sister, Terri Chung, who added that he is now too weak to work.
He was detained in November as he led a tour group through the northern region of the country.
His sentencing came amid acrimonious relations between the regime of Kim Jong-un and Washington over the state's nuclear programme.
Chung said she learned of her brother's transfer from the Swedish ambassador to North Korea, who visited Bae on Friday. The ambassador, who has met with Bae a handful of times since his detention, has been his only foreign visitor, Chung said.
Chung's comments came at a prayer vigil for Bae at a church in the family's home city of Seattle on Saturday evening. The event was attended by more than 100 friends, relatives and supporters.
His sister also read from a letter sent by Bae to his supporters written on 13 June, in which he encouraged them to push his case with American officials.
"The only way I can be free to return home is by obtaining amnesty," Bae wrote.
"In order for that to happen it will take more active efforts from the U.S. government side."
Two American journalists arrested in 2009 by North Korea and detained until former President Bill Clinton traveled there to negotiate their release were organizing a solidarity vigil in New York, one of the journalists, Euna Lee said.
North Korea has in the past used the release of high-profile American prisoners as a means of garnering a form of prestige or acceptance by portraying visiting dignitaries as paying homage to the country and its leader.
An Internet petition started by Bae's son urging President Barack Obama to secure a "Special Amnesty" for Bae has garnered nearly 8,000 signatures.
Reports last month that former President Jimmy Carter was set to visit North Korea to negotiate for Bae's release were ultimately denied as false.