Brazil's government has summoned the US ambassador and called a cabinet meeting over allegations that the National Security Agency directly spied on President Dilma Rousseff and her Mexican counterpart.
The claims reported by US journalist Glenn Greenwald, who obtained secret files from NSA leaker Edward Snowden, follow allegations of widespread US electronic espionage in Latin America that angered the region's leaders.
The report emerged as Rousseff prepares to travel to Russia later this week for a Group of 20 summit during which she will come face to face with US President Barack Obama. She is also scheduled to visit Washington in October.
Greenwald, who lives in Rio de Janeiro and writes for London's Guardian newspaper, told Globo television that the NSA tracked Rousseff's use of the internet and accessed emails of Mexican President Enrique Pena Nieto before his election last year.
A Brazilian foreign ministry spokesman said US Ambassador Thomas Shannon "was called to explain" the new allegations. The US embassy declined to comment and a State Department spokeswoman in Washington said she was looking into the matter.
"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.
Rousseff called a cabinet meeting that will include her ministers of defence, foreign affairs and justice.
"We are in an emergency situation due to these spying allegations," presidential chief of staff Gilberto Carvalho was quoted as saying by O Estado de Sao Paulo newspaper.
A spokesman for Pena Nieto declined to comment and said any reaction would be released in a statement.
