The journalist who first published the contents of classified documents provided by ex-National Security Agency contractor Edward Snowden, told a Brazilian TV show Sunday that personal emails from the presidents of Brazil and Mexico had been spied on.
Glenn Greenwald told Globo news program "Fantastico" that a document dated June 2012, showed that Mexican President Enrique Pena Nieto's emails were being read one month before he was elected to office.
Greenwald, who writes for the U.K.-based Guardian newspaper but lives in Rio de Janeiro, said the emails included communications from Nieto indicating who he would name in his Cabinet.
He also reported that the NSA collected the data through an undefined association between U.S. and Brazilian telecommunications companies.
The journalist told the Associated Press, in an email, that the document did not contain any specific messages intercepted from Brazilian President, Dilma Rousseff.
However, it did reveal which aides she had communicated with, and tracked patterns of how those aides communicated among one another and with third parties.
"It is clear in several ways that her communications were intercepted, including the use of DNI Presenter, which is a program used by NSA to open and read emails and online chats," he told the AP.
Brazilian Justice Minister Eduardo Cardozo told the O Globo newspaper that if the facts of the story were confirmed, they should be considered very serious” and "a clear violation of Brazilian sovereignty.”
“Given these facts, we will require formal explanation to the U.S. government, the Foreign Ministry will summon the U.S. ambassador (Thomas Shannon) to give explanations,” he said, adding the country may take the matter to the U.N..
Mexico's Foreign Ministry said they had no comment.
Greenwald's revelation came days after a British court ruled that authorities in the U.K. could sift through documents seized from his partner, David Miranda, who was detained by authorities at London’s Heathrow airport for nine hours.
Miranda, who was in transit from Berlin to Brazil, was released without charge minus his laptop, phone and memory sticks.
His lawyer has requested an injunction to prevent the authorities from examining any data seized from Miranda and has also started legal action to ask judges to rule that his detention was illegal.
But two judges at Britain's High Court said the authorities could continue to look at the information until August 30, for the defense of national security and for the purposes of investigating whether the claimant is a person who is or has been concerned with the commission, preparation or instigation of acts of terrorism.
The Associated Press contributed to this report.