In what they are calling “the most classified documents ever released by a news organization,” WikiLeaks announced the publication of cables marked “Top Secret” on Tuesday, detailing National Security Agency surveillance of foreign leaders.

The document dump revealed the interception of climate talks between UN Secretary Ban-ki Moon and German Chancellor Angela Merkel before the 2009 Copenhagen Conference, as well as the long-term interception of the phone of Johann Human, the Director of the Rules Division of the World Trade Organisation (WTO), and five other top EU economic officials.

Also included are intercepted Italian diplomatic cables from 2011 that detail how Israel’s Prime Minister Benjamin Netanyahu implored Italy's Prime Minister Silvio Berlusconi to help patch up his strained relationship with President Barack Obama.

"Netanyahu insisted that the trigger for the dispute—Israel's decision to build 1,600 homes in contested East Jerusalem—was totally in keeping with national policy dating back to the administration of Golda Meir, and blamed this mishandling on a government official with poor political sensitivity," the NSA cable reads. "Berlusconi promised to put Italy at Israel's disposal in helping mend the latter's ties with Washington."

A document also revealed that, during a private meeting, Berlusconi "was told the Italian banking system was ready to 'pop like a cork.'"

Following the release of the cables, Italy’s Foreign Ministry called on their US ambassador to clarify the report.

"The Italian Foreign Ministry has summoned the U.S. ambassador, John Phillips, to clarify the news appeared (in) the press, according to which the Italian Prime Minister Silvio Berlusconi and some of his close collaborators would have been subject to wiretaps in 2011," the ministry wrote in a statement.

The State Department has denied the contents of the cables.

"As we have said previously, we do not conduct any foreign intelligence surveillance activities unless there is a specific and validated national security purpose," US State Department deputy spokesman Mark Toner told CNN on Tuesday. "This applies to ordinary citizens and world leaders alike.

"Indeed, (President Barack Obama) has made clear that — unless there is a compelling national security purpose — we will not monitor the communications of heads of state and government of our close friends and allies."

Toner went on to claim that the US and Italy have a long friendship and history of working together to advance mutual interests globally.

"Today we showed that UN Secretary General Ban Ki-Moon'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 a statement on the website.

"The U.S. government has signed agreements with the UN that it will not engage in such conduct against the UN—let alone its Secretary General," he said. "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."