Police in Mongolia have arrested a senior member of a nationalist group in connection with the slaying last week of a volunteer with the Japan International Cooperation Agency.

The body of Shin Kawasaki, 69, of Tokyo, was found Wednesday in a water-filled bathtub with his legs tied and his residence ransacked.

A senior police official said that when he was arrested, the suspect was in possession of a personal computer stolen from Kawasaki's home.

The man has admitted to robbing and killing Kawasaki, the official said. The suspect said he acted alone and he did not know Kawasaki.

A former freelance broadcast writer, Kawasaki was sent to Mongolia in October 2005 for a two-year stint to instruct the country's public broadcaster on program development, JICA said. His family did not go with him.