Brazil announces it will demand an explanation from the US after allegations that the National Security Agency (NSA) spied on Brazilian government communications.

The allegations were made by Rio-based journalist Glenn Greenwald in a programme on TV Globo on Sunday.

Glenn Greenwald obtained secret files from whistle-blower Edward Snowden.

Communications from the Mexican president were also accessed by the NSA, Glenn Greenwald said.

Glenn Greenwald, a columnist for the Guardian newspaper, told TV Globo’s news programme Fantastico that secret documents leaked by Edward Snowden showed how US agents had spied on communications between aides of Brazil’s President Dilma Rousseff.

Brazil’s Justice Minister Jose Eduardo Cardozo said that “if these facts prove to be true, it would be unacceptable and could be called an attack on our country’s sovereignty”.

According to the report, the NSA also used a program to access all internet content that President Dilma Rousseff visited online.

Edward Snowden’s documents showed how US agents had spied on communications between aides of Brazil’s President Dilma Rousseff

The report also alleges that the NSA monitored the communications of Mexican President Enrique Pena Nieto before he was elected.

Glenn Greenwald said that a document dating from June 2012 showed that Enrique Pena Nieto’s emails were being read.

A spokesman for the Mexican foreign ministry told the Agence France Presse news agency that he had seen the report but had no comment.

The documents were provided to Glenn Greenwald by ex-US intelligence analyst Edward Snowden, who was granted temporary asylum in Russia after leaking secret information to media in the US and Britain.

Glenn Greenwald was the first journalist to reveal the secret documents leaked by Edward Snowden on June 6. Since then, he has written a series of stories about surveillance by US and UK authorities.

The detention last month for nine hours at London’s Heathrow airport of Glenn Greenwald’s partner, David Miranda, caused widespread controversy in the UK and abroad.

Glenn Greenwald said the detention of his partner amounted to “bullying” and was “clearly intended to send a message of intimidation” to those working on the NSA revelations.

The British government said that it was right for the police to act if they believed that someone had “highly sensitive stolen information”.

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