Brasilia, Sep 4 (IANS): Brazil's Senate has formed an Investigative Parliamentary Commission to follow up on reports that the US National Security Agency (NSA) spied on President Dilma Rousseff.

"We intend to protect national sovereignty," said Senator Vanessa Graziotin, of the Communist Party of Brazil. The committee was formed Tuesday, reports Xinhua.

The committee comprises 11 main members and seven substitutes, and initially will have 180 days to investigate claims that the NSA monitored emails between Rousseff and several of her top aides and tapped her phone.

The period of investigation can be extended by 180 more days if the probe body needs more time.

As the committee's first order of business, members discussed the possibility of the state providing federal protection for Rio de Janeiro-based journalist Glenn Greenwald and his partner David Miranda, considering they are the key witnesses in the investigation.

Greenwald was the first to break the story of Washington's global spying programme, based on documents leaked by former NSA contractor Edward Snowden.

Snowden, who is wanted by the US on espionage charges for revealing the surveillance scheme, has been given temporary asylum in Russia.

Miranda was recently interrogated for nine hours at London's Heathrow airport as he travelled from Germany to Brazil, and had his belongings confiscated. British officials had said they were operating under an anti-terror law, but Greenwald said he believed it was an attempt to intimidate.

The Senate's decision to open an investigation follows the broadcast Sunday of a Brazilian television news programme reporting that the NSA spied on the highest levels of Brazil's government, even targeting the president.

That report was also based on documents leaked by Snowden and made public by Greenwald.

News of NSA spying on Brazil first broke in July, when Brazil's O Globo daily published articles alleging that the agency had monitored digital communications and phone calls.