The documents leaked by whistleblower Edward Snowden reportedly indicate that the US' National Security Agency apparently snooped on telephone conversations of as many as 35 world leaders.
The 'US fugitive' claims that the spy agency NSA obtained the phone numbers from an official in another American government department.
The latest allegations come amidst the recent protest by German chancellor Angela Merkel who demanded answers from the US President Barack Obama over claims that her own conversations were being snooped on.
According to Mirror, the leaked documents suggest that the NSA encouraged senior officials in departments such as the White House, the State Department and the Pentagon to provide access to their 'Rolodexes' containing the phone numbers of leading foreign politicians.
The report said that one US official was said to have passed on 200 numbers, including those of the 35 world leaders, who were immediately 'tasked' for monitoring by the NSA.
The revelations by Snowden have distressed US' relations with its allies over breach of trust as leaders are not only aggressively seeking justifications of the alleged snooping but also threatening to cancel crucial meetings with Obama.
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French president Francois Hollande has earlier called Obama to confront him over similar allegations, while UK Prime Minister David Cameron too had been under the claims of being snooped upon.
However, the Obama administration has denied the allegations against Merkel in a cleverly worded statement that the agency is not and will not monitor the respective leader's calls, but did not make it clear if the practice was done in the past.
The report added that Britain, the US, Canada, Australia and New Zealand are members of the so-called 'Five Eyes' group, who share signals intelligence and are supposed not to spy on each other.