Authorities probe threats against Caroline Kennedy in Japan

US Ambassador to Japan Caroline Kennedy looks on before a welcome dinner hosted by Japanese Prime Minister Shinzo Abe (not pictured) at Abe's residence in Tokyo, March 17, 2015. [Photo/Agencies]

WASHINGTON - American and Japanese authorities are working to ensure the safety of US personnel in Japan after media reports of death threats against US Ambassador Caroline Kennedy and another American diplomat, the US State Department said on Wednesday.

The US Embassy in Tokyo received the threats by telephone last month, with several phone calls made by an English-speaking man, the Yomiuri Shimbun newspaper reported, citing a Tokyo police official.

The threats also targeted the US consul general in Okinawa, Alfred Magleby, according to Yomiuri and other Japanese and US media reports. Okinawa island is known in Japan as host to the bulk of US service personnel stationed in the country.

State Department spokeswoman Jen Psaki did not confirm any specific threats to Kennedy and Magleby, but she said in a statement, "We take any threats to US diplomats seriously."

"We are working with the Japanese government to ensure the necessary measures are in place," she said.

The US Embassy and Tokyo Metropolitan Police Department declined to comment.

Reports of the threats emerged as first lady Michelle Obama arrived in Japan on Wednesday for a three-day visit, including a meeting with diplomatic staff from Tokyo and Osaka.

The reports came two weeks after the US ambassador to South Korea, Mark Lippert, was attacked and injured by a man with a knife during an event in Seoul.

That prompted debate about threats against American diplomats abroad and the precautions taken to protect US ambassadors. The State Department has said security for Lippert was adequate.

Security for US ambassadors worldwide is based on assessments by experts from the State Department's Bureau of Diplomatic Security, according to the department.

Lippert had been assigned a single South Korean National Police bodyguard but his security was increased after the attack to include several other police officers, the State Department has said.

Earlier this month, department spokeswoman Marie Harf said she was not aware of plans to boost diplomatic security elsewhere in the world following the attack.

It was not clear what security arrangements have been provided for Kennedy, the daughter of former US President John F. Kennedy. She began her assignment in Japan in November 2013.