Last Updated Mar 18, 2015 7:10 AM EDT
TOKYO -- Japanese police are investigating phone calls threatening to kill U.S. Ambassador Caroline Kennedy and another American envoy, authorities said Wednesday.
Tokyo police are investigating calls to the U.S. Embassy threatening to kill Kennedy and similar ones targeting Alfred Magleby, the U.S. consul general based on the southern island of Okinawa, an Okinawa police official said on condition of anonymity because he was not authorized to comment on an investigation by Tokyo authorities.
Tokyo police declined to comment. The embassy also did not comment, citing policy regarding the ambassador's security.
Okinawa is home to about half of the 50,000 American troops based in Japan.
CBS News correspondent Seth Doane says protests regularly pop up in Okinawa over the large U.S. troop presence, but they are peaceful.
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.
Earlier this month, the U.S. Ambassador to South Korea, Mark Lippert, was knifed by an anti-U.S. activist in Seoul and had to be hospitalized for several days.
Doane says Kennedy, the daughter of John F. Kennedy, is a high-profile figure in Japan and generally mixes freely with crowds during public outings.
She is expected to meet this week with first lady Michelle Obama, who arrived to Tokyo on Wednesday to promote the White House's "Let Girls Learn" education initiative.
