The Democratic People's Republic of Korea will put a detained US citizen on trial on Sept 14, state media said on Sunday, less than a week after Matthew Miller made a highly unusual televised plea for help from Washington.

Miller, one of three US citizens being held in the DPRK, was arrested in April after Pyongyang said he ripped up his visa at immigration and demanded asylum.

"The Supreme Court of the DPRK decided to hold on Sept 14 a court trial on American Matthew Todd Miller, now in custody according to the indictment of a relevant institution," the KCNA news agency said.