The Governor of the Northern Marianas, Eloy Inos, has written to Japan's Foreign Minister regarding the discovery of graffiti on Japanese War memorials on Saipan.
The letter says the CNMI government has made sure the graffiti has been removed and that Mr Inos and the government takes the vandalism seriously.
The letter follows an article in the Japanese Sankei newspaper about disrespectful graffiti, in Chinese characters, being discovered on the memorials.
Japan is one of the Northern Marianas' largest tourism markets, with a number of Japanese tourists visiting memorials to remember those who perished during the second world war.
