Whistleblowing website WikiLeaks has accused the United States of spying on Japanese cabinet officials, banks and companies, including the Mitsubishi conglomerate.
According to the BBC, documents released by WikiLeaks list 35 telephone numbers targeted for interception by the United State's National Security Agency (NSA) although there has been no comment from Japan on the latest claims.
WikiLeaks further said that the surveillance extends back to at least eight years.
The documents, marked 'top secret', reportedly show that the United States was listening in on conversations at Japanese ministries and offices, including Bank of Japan officials and the fossil fuel departments at Japanese firms Mitsubishi and Matsui.
It stated the move was an attempt on the part of the United States to become aware of Japan's internal discussions on issues such as trade talks, climate change policies and nuclear and energy policies - as well as the contents of a confidential briefing in Prime Minister's Shinzo Abe's residence.
Wikileaks has previously released files showing the United States spying on Germany, France and Brazil.