In spite of NSA's insistence that they do not engage in industrial espionage, Brazilian President Dilma Rousseff has said that leaked "intelligence documents" appear to run counter to US claims.

The NSA told the Washington Post in an emailed statement late last month: “The Department of Defense does engage” in computer network exploitation," adding: "The department does ***not*** engage in economic espionage in any domain, including cyber."

Brazilian TV news programme Fantástico alleged that the NSA had monitored the internal network of Petrobras, the part-government-owned energy giant, based on leaked NSA reports.

Documents from Glenn Greenwald feature Petrobras's name as an example of targets of the Blackpearl programme, which extracts data from private networks. Petrobras is the part-government-owned energy giant in Brazil.

Glenn Greenwald is the journalist to whom NSA whistleblower Edward Snowden had revealed certain leaked documents.

The US government has said that its surveillance activities are about foreign policy and fighting terrorism and nothing to do with industrial or economic espionage.

The NSA allegedly bugged the telephones and internet communications of Brazil's President Dilma Rouseff and her key staffers.