The United States' National Security Agency (NSA) spied on UN Secretary General Ban Ki-Moon's meeting with German Chancellor Angela Merkel on the climate change issue, as well as on Israel Prime Minister Netanyahu's meeting with Italian Prime Minister Berlusconi, WikiLeaks said Tuesday.

WikiLeaks released "highly classified" documents Tuesday, stating that the NSA had bugged meetings between Ban Ki-moon and Merkel when the leaders had met to discuss the issue of climate change, with the intention of "protecting its largest oil companies."

"Today we showed that UN Secretary General Ban KiMoon's private meetings over how to save the planet from climate change were bugged by a country intent on protecting its largest oil companies," WikiLeaks founder Julian Assange said in the WikiLeaks report. 

The NSA also spied on a private meeting between former French President Nicolas Sarkozy, Merkel and Berlusconi, in which Sarkozy told the Italian leader that "the Italian banking system would soon pop like a cork," the WikiLeaks report said. 

The United States also spied on Netanyahu when he met with Berlusconi, during which the former allegedly "begged" with the later for help on how he should "deal" with US President Barack Obama. Last year, US officials had accused Israel of spying on US-led talks with Iran on the nuclear deal.

Assange said he awaited the United Nations's reaction on the leaked reports. 

"It will be interesting to see the UN's reaction, because if the Secretary General can be targeted without consequence then everyone from world leader to street sweeper is at risk," he said. "We previously published Hillary Clinton orders that US diplomats were to steal the Secretary General's DNA. The US government has signed agreements with the UN that it will not engage in such conduct against the UN--let alone its Secretary General."

Assange faces serious criminal charges in the United States for publishing secret US diplomatic cables.