U.S . Ambassador to Japan , Caroline Kennedy , waves before she delivers opening remarks during an appearance at Waseda University in Tokyo on Wednesday . Japanese police were investigating phone calls threatening to kill U.S . Ambassador Caroline Kennedy and another American envoy , authorities said on Wednesday . Tokyo police were 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 , according to police sources . Tokyo police declined to comment . The embassy also did not comment , citing policy regarding the ambassador 's security . Kennedy was due to meet with First Lady Michelle Obama on her arrival in Tokyo on Wednesday to promote her 'Let Girls Learn ' education initiative . Obama 's arrival coincided with a speech made by former U.S. President Bill Clinton at a Tokyo university on Wednesday afternoon alongside Kennedy and Japanese Prime Minister Shinzo Abe as they attended a symposium on the legacy of assassinated John F. Kennedy . Okinawa is home to about half of the 50,000 American troops based in Japan . 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 . Kennedy was due to meet with First Lady Michelle Obama on her arrival in Tokyo on Wednesday ( pictured ) to promote her 'Let Girls Learn ' education initiative . CBS reported that JFK 's daughter was often seen mixing freely with crowds during her high-profile outings in Japan . The State Department said in a statement on Thursday : 'We take any threats to U.S. diplomats seriously . 'We take every step possible to protect our personnel . We are working with the Japanese government to ensure the necessary measures are in place . We will not comment on the specific details of any threats or the steps we take to address them . ' 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 . Lippert suffered a deep facial gash and stab wound to his wrist after being attacked by a knife-wielding pro-North Korean activist during a breakfast forum . Former US President Bill Clinton was also in attendance at the Tokyo event on Wednesday . Here , he bids a farewell to the audience after delivering a keynote speech at the JFK International Symposium held at Waseda University . Injured U.S . Ambassador to South Korea Mark Lippert , center , gets into a car to leave for a hospital in Seoul , South Korea on March 5 after being attacked by a man wielding a razor .
Tokyo police were investigating calls to the U.S. Embassy threatening to kill Kennedy . Similar calls were made targeting Alfred Magleby , the U.S. consul general based on the southern island of Okinawa . Japanese media reports said death threats came last month from a caller speaking in English , and that police suspected blackmailing .