Brasilia: The US ambassador to Brazil was summoned by authorities Monday over new allegations that the US National Security Agency spied on President Dilma Rousseff, an official said.
US journalist Glenn Greenwald, a Guardian newspaper columnist who obtained secret files from NSA leaker Edward Snowden, told Globo television that the agency snooped on the communications of Rousseff and Mexican President Enrique Pena Nieto.
A Brazilian foreign ministry spokesman said US Ambassador Thomas Shannon "was called to explain" the claims made by Greenwald, who is based in Rio de Janeiro.
"If these facts prove to be true, it would be unacceptable and could be called an attack on our country's sovereignty," Justice Minister Jose Eduardo Cardozo said.
A spokesman for Pena Nieto declined to comment and said any reaction would be released in a statement.
Greenwald told Globo on Sunday that a document dated June 2012 shows that Pena Nieto's emails were being accessed, one month before he was elected.
The NSA also intercepted some of Pena Nieto's voicemails. The communications included messages in which the future leader discussed the names of potential cabinet members.
As for Rousseff, the NSA said in the document that it was trying to better understand her methods of communication and interlocutors using a program to access all Internet content the president visited online.
Rousseff, who is due to make a state visit to Washington in October, held a working meeting to study the revelations in the Globo report, the channel said.
The NSA program allegedly allows agents to access the entire communications network of the president and her staff, including telephone, Internet and social network exchanges.
Cardozo met with US Vice President Joe Biden in Washington last week to discuss the matter.
The United States has rejected a Brazilian offer to negotiate a bilateral agreement on surveillance.
In July, Greenwald co-wrote articles in O Globo newspaper revealing that the US government had a joint NSA-CIA base in Brazil to gather data on emails and calls flowing through the country.
Snowden, a former NSA contractor, is now a fugitive in Russia under temporary asylum.
He is wanted by Washington on espionage charges linked to media disclosures about US surveillance programs.