SEOUL, May 2 (Yonhap) -- North Korea has relocated three American detainees from a labor camp to a hotel on the outskirts of Pyongyang ahead of a planned summit between leader Kim Jong-un and President Donald Trump, a South Korean activist said Wednesday.

The U.S. citizens -- Kim Hak-song, Tony Kim and Kim Dong-chul -- were moved in early April following instructions from superior authorities, said Choi Sung-yong, head of a group for families of South Koreans abducted by North Korea, citing a resident in Pyongyang.

The detainees have been accused of espionage or "hostile acts."

Washington and Pyongyang are known to be in talks over their possible repatriation.

Last year, Otto Warmbier, an American college student who was arrested in North Korea for allegedly removing a political poster from a hotel in Pyongyang, died shortly after being returned to the U.S. in a coma.