Japanese police are investigating phone calls threatening to kill US Ambassador to Japan Caroline Kennedy and another American envoy.
The police are investigating threats made to kill Kennedy and Alfred Magleby, the US consul general based on the southern island of Okinawa.
Japanese media reports said that the death threats came last month from a caller speaking in English, and that police were looking into the case on suspicion of blackmailing.
No other details, including motives, were known.
There are about 50,000 American troops based in Japan and Okinawa is home to about half of them.
