Three Japanese had been detained in the Democratic People's Republic of Korea (DPRK) for drug trafficking and currency counterfeiting and one of them were already expelled out of the country, the KCNA said on Wednesday.

The two in custody were undergoing judicial process, the report said.

The three Japanese, who entered the country from the northwestern city of Rosan on March 14 this year and worked for three companies, already pleaded guilty. "They admitted their criminal acts and their seriousness," the KCNA said.

The activities of the Japanese are grave crimes that "severely violate the DPRK law and related international laws" and they should be held responsible for what they did, said the report.

Last month, Japan's media reported that two Japanese people were taken into custody and another was expelled while visiting the DPRK's special economic zone in Rason.