TOKYO - Tokyo is seeking an explanation from Washington over alleged US spying on the Japanese government and companies, local media reported on Monday.

"We are strongly asking US Director of National Intelligence (James) Clapper to check the facts," Chief Cabinet Secretary Yoshihide Suga told reporters over the US National Security Agency's alleged interception.

"If (the alleged spying) were true, Japan, as an ally (of the United States), would find it extremely regrettable," Japan's Kyodo News Agency citing Suga as saying.

The Wikileaks website on Friday posted NSA reports and a list of 35 Japanese targets for telephone intercepts, including the Japanese Cabinet Office, the Bank of Japan, the country's finance and trade ministries, and major Japanese trading companies.

According to the website, the eavesdropping dated back to Prime Minister Shinzo Abe's first government in 2006, and one report from telephone intercepts of senior Japanese officials could have been shared with Australia, Canada, Britain and New Zealand - the US intelligence partners.

Asked about Japan's security measures for secret information, the top government spokesman said, "I believe such secrets will never be leaked because (the government) is taking all possible measures (to prevent leaks)."

WikiLeaks has also released similar reports about the United States spying on Germany, France and Brazil, which have strained diplomatic relations with those countries.