Japanese police are investigating death threats against U.S. Ambassador Caroline Kennedy and one other American diplomat.

Tokyo police say that they have received calls in English from a source threatening to kill Kennedy, in addition to similar threats targeting consul general Alfred Magleby.

FoxNews.com reported:

Japanese media reported that the calls to the embassy were made last month by a man who spoke English. The reports suggested that the threats may have been tied to a scheme to blackmail Kennedy or the embassy. There has been no comment from the embassy or the State Department.

The threats against Kennedy have been made public 13 days after Mark Lippert, the U.S. envoy to South Korea, was attacked and injured by a knife-wielding assailant. South Korean police said the attacker had targeted Lippert to protest joint military drills conducted by the U.S. and South Korea.

Kennedy, 57, is the daughter of former President John F. Kennedy. She assumed the Tokyo post in 2013.

Watch more in the "Fox and Friends" clip above.

You might also be interested in ...

Peters: 'If Obama Developed Athlete's Foot, He Would Blame Bush'

WATCH: Deputies Pull Woman Through Window of Burning Home

Sculpture Made From WTC Beams Unveiled in London to Honor 9/11 Victims

These 13 States Want to Allow College Students to Carry a Gun