According to WikiLeaks' "Target Tokyo" release, the NSA targeted Japanese companies, senior government officials, governmental advisors and even Premier Shinzo Abe from at least September 2006 to September 2007.
Moreover, one of the interception reports might have been shared with the governments of Australia, Canada, Britain and New Zealand.
"If this is true, it is extremely regrettable. We need to lodge a protest. But the Japanese government first must verify it," an anonymous Japanese official said, as cited by Xinhua.
The NSA telephone interception target list included the Japanese Cabinet Office, the central bank as well as the finance and economy ministries, and the executive secretary of Chief Cabinet Secretary Yoshihide Suga.
The new scandal might damage the relations between the United States and Japan.
Japan is the latest NSA target uncovered by WikiLeaks, which recently published documents implicating the agency in eavesdropping on French, Saudi and German high-ranking officials.