Japanese officials were investigating death threats made against U.S. Ambassador to Japan Caroline Kennedy and another American diplomat in the country, local media reported on Wednesday.
The reports came out on the same day that Michelle Obama arrived in Japan, her first stop on a trip to Asia aimed at highlighting the importance of girls' education.
The embassy received "several" telephone calls last month threatening to kill Kennedy and Alfred Magleby, the U.S. Consul General in Okinawa, a senior official at the Tokyo Metropolitan Police told Yomiuri Shimbun newspaper. Around 25,000 U.S. troops are based in the island of Okinawa.
Japanese and American officials declined to comment on the reports. Tokyo Metropolitan officials were investigating the calls, according to public broadcaster NHK. A police source told Yomiuri Shimbun that the phone calls were made by a man speaking in English.
Ambassador Kennedy is the daughter of late President John F. Kennedy and Jacqueline Kennedy.
This article originally appeared on NBCNews.com.