The Japanese government has remained relatively silent since the WikiLeaks website published documents Friday showing the U.S. National Security Agency (NSA) has spied on the Japanese government and Japanese companies.

The documents, dated from 2007 to 2009, include five NSA reports -- four of which are marked top-secret -- that provide intelligence on Japanese positions on international trade and climate change.

WikiLeaks also posted an NSA 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 Associated Press, while claiming that "Japan will continue to employ all the necessary measures to protect (its) information," Japanese Foreign Ministry press secretary Yasuhisa Kawamura declined to provide details on what he called the communication about the issue of NSA "information collection" between Japan and the United States.

The U.S. embassy in Tokyo said it was aware of the report but would not say anything further. Mitsui also declined comment, and Mitsubishi did not return a call.

U.S. State Department deputy spokesperson Mark Toner said the U.S. government has not received any formal or informal protests from Japan.

"We do not think Japan will take this as a problem," said Toner.

The Japanese public has voiced disappointment over and objection to the spying incident despite little coverage of it by Japanese media inside Japan.

Most Japanese find it hard to accept that "a friendly ally would spy on Japan" although some say "it is not strange for a country like the United States to act this way."

"What the United States did would gravely breach the trust between the two countries," a netizen posted his comment on the website.

"Why is Japan being so submissive? Can't we lodge a protest?" another netizen asked.

Spying among friendly countries is classic tradecraft but the sweep and scope of the NSA program have surprised allies and raised indignation among those targeted: France, Germany, Mexico and Brazil among others.

However, unlike Japan, the other victim countries have strongly protested being spied on.

On Oct. 21, 2013, France demanded an explanation from Washington over a report that the United States swept up 70 million French telephone records and text messages in its global surveillance net, even recording certain private conversations.

In the meantime, the Elysee Palace issued a strongly worded statement afterwards, expressing "profound reprobation" over U.S. actions that it said intruded on the private lives of French citizens.

Two says later, Germany Chancellor Angela Merkel called U.S. President Barack Obama to demand clarification, a move that showed how seriously Berlin was taking the issue, which has caused outrage in Germany.

"This is not how you should treat your partners," said 38-year-old German Stephanie Hilebrand. "We're not terrorists, nor is our chancellor."

The question of mass U.S. spying on its allies has sparked an international debate over the limits of American spying after revelations from Edward Snowden, the fugitive former U.S. intelligence operative. The strongest objection has come from Brazil.

Brazilian President Dilma Rousseff canceled a state visit to Washington over a dispute involving Brazil's desire to question Snowden after information he leaked indicated that the U.S. side intercepted Rousseff's communications with aides, hacked a state-run oil company's computer network and snagged data on emails and telephone calls flowing through Brazil.