Brazil’s President Dilma Rousseff, on Monday, accused the U.S. of snooping on Brazil’s state-run oil firm, Petroleo Brasileiro Petrobras SA (NYSE:PBR), for “economic and strategic” reasons and not for national security.

The U.S. National Security Agency, or NSA, allegedly spied on computer networks of companies, including Petrobras, according to Brazil’s Globo television network, which cited documents obtained by former defense contractor Edward Snowden.

Rousseff said "if the facts are confirmed, it would be clear the espionage was not for security or the fight against terrorism, but to respond to economic and strategic interests. Without doubt, Petrobras is not a threat to the security of any country," she said in a statement, according to news reports. "The Brazilian government is determined to get clarification from the US government ... and require specific action to remove the possibility of espionage once and for all," Rousseff said.

Petrobras said on Monday that its computer networks are secured against spying.

Brazil, which is upset over last week’s reports that NSA spied on Rousseff and her Mexican counterpart, Enrique Pena Nieto, has demanded a formal apology from the U.S. government, and the latest report of alleged spying on state-run Petrobras is likely to further complicate U.S.-Brazil ties.

NSA also spied on systems operated by Google Inc (NASDAQ:GOOG), the French foreign ministry, and the Society for Worldwide Interbank Financial Telecommunication, or SWIFT, an international bank cooperative, Reuters reported, citing an NSA presentation, dated May 2012 and aired by Globo TV.

The presentation also contained instructions to new NSA agents on how to spy on private computer networks, but it did not specify the nature of the data that NSA may have been seeking, Reuters reported.

James Clapper, director of U.S. National Intelligence, said earlier on Monday that U.S. agencies gathered information about economic and financial matters in order to identify sources of terrorist financing and to predict financial crises and disruption of financial markets, Reuters reported.

“What we do not do is use our foreign intelligence capabilities to steal the trade secrets of foreign companies on behalf of - or give intelligence we collect to - U.S. companies to enhance their international competitiveness or increase their bottom line,” Clapper said.

Glenn Greenwald, a reporter for The Guardian, who interviewed Snowden and reported in detail about the U.S. government’s surveillance programs, told Globo that documents he received from Snowden contained “much more information on spying on innocents, against people who have nothing to do with terrorism, or on industrial issues, which need to be made public,” according to Reuters.

The report that NSA snooped on Petrobras appeared to contradict a statement made by an NSA spokesman and published on Aug. 30 by the Washington Post.

“The Department of Defense does engage” in computer network exploitation, a spokesman for NSA, which belongs to the Defense Department, said in an email to the Washington Post. “The department does ***not*** engage in economic espionage in any domain, including cyber.”

President Barack Obama, who met with Rousseff and Pena Nieto at the international summit of the world’s top 20 economies, or the G-20, in St. Petersburg on Friday, discussed reports that NSA intercepted their email and other online communication, and promised to investigate the alleged spying, Reuters reported.

“I assured them that I take these allegations very seriously. I understand their concerns. I understand the concerns of the Mexican and Brazilian people; and that we will work with their teams to resolve what is a source of tension,” Obama said at a news conference.