Bae's sister, Terri Chung, said the 45-year-old missionary has diabetes and an enlarged heart and apparently had taken a turn for the worse that made him too weak to remain at the North Korean labor camp.
"We are terribly worried about his health," Chung told KING-TV in her hometown of Seattle. "I think it has been deteriorating."
Bae was sentenced in May to 15 years of hard labor after being convicted of plotting to overthrow the North Korean government. He was accused of using his tourism business as a front for organizing group hostile to the Pyongyang regime, the BBC said.
Chung said she got the word about her brother from a Swedish diplomat.
Chung and Bae's supporters held a rally at the Quest Church in Seattle Saturday to urge the Obama administration to step up its efforts to win his release. "I firmly believe he will come home, and not in 15 years," she said. "I hold onto faith in my God and in my government."
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