Australia is receiving secret US intelligence on Japanese trade negotiations, according to newly published WikiLeaks documents.
The Saturday Paper has reported the US National Security Agency routinely obtains highly sensitive information on issues including US-Japanese relations, trade issues and climate change policy.
The information, some of which is collected from discussions in Prime Minister Shinzo Abe's official residence, is shared with Australia, the newspaper says.
Another NSA target is the minister for economy, trade and industry, Yoichi Miyazawa.
Major Japanese companies such as Mitsubishi's natural gas division and Mitsui Corporation are also being targeted.
The US, Japan and Australia are currently involved in talks in Hawaii to conclude the Trans-Pacific Partnership free trade agreement.
Japan is one of Washington's key allies in the Asia-Pacific region and they regularly consult on defence, economic and trade issues, French news agency AFP reports.
"The reports demonstrate the depth of US surveillance of the Japanese government, indicating that intelligence was gathered and processed from numerous Japanese government ministries and offices," WikiLeaks said on Friday (local time).
"The documents demonstrate intimate knowledge of internal Japanese deliberations" on trade issues, nuclear and climate change policy, and Tokyo's diplomatic relations with Washington, it said.
The group also pointed to intercepts about "sensitive climate change strategy" and the "content of a confidential prime ministerial briefing that took place at [Prime Minister] Shinzo Abe's official residence".
There is no specific mention of wiretapping Abe, but senior politicians were targeted, including Miyazawa, while Bank of Japan governor Haruhiko Kuroda was also in the sights of US intelligence, WikiLeaks said.
There was no immediate reaction from Tokyo, AFP reported.
The claims of spying on trade officials come at a particularly sensitive time as the US, Japan, Australia and nine other Pacific Rim countries look to finalise the TPP, the most ambitious trade deal in decades.
But Washington and Tokyo, by far the biggest economies in the negotiations, have sparred over car sector access and Tokyo's bid to protect agricultural products from the proposed Trans-Pacific Partnership.
The spying goes back at least as far as Abe's brief first term, which began in 2006, WikiLeaks said. Abe swept to power again in late 2012.
The whistleblower group said four reports were classified as "Top Secret" while one was marked to indicate it could be released to allies Britain, Australia, Canada and New Zealand.
"In these documents we see the Japanese government worrying in private about how much or how little to tell the United States, in order to prevent undermining of its climate change proposal or its diplomatic relationship," WikiLeaks editor-in-chief Julian Assange said in a statement.
"And yet we now know that the United States heard everything and read everything, and was passing around the deliberations of Japanese leadership to Australia, Canada, New Zealand and the UK."