Media playback is unsupported on your device Media caption Former CIA worker Edward Snowden was last seen in Hong Kong, reports the BBC's Jennifer Pak

The EU is demanding assurances that Europeans' rights are not being infringed by massive, newly revealed US surveillance programmes.

Justice Commissioner Viviane Reding plans to raise the concerns with US Attorney General Eric Holder on Friday.

Last week a series of leaks by a former CIA worker led to claims the US had a vast surveillance network with much less oversight than previously thought.

The US insists its snooping is legal under domestic law.

The Obama administration is investigating whether the disclosures by former CIA worker Edward Snowden were a criminal offence.

More revelations promised

Mr Snowden's employer, defence contractor Booz Allen Hamilton, said on Tuesday it had fired the 29-year-old infrastructure analyst for violating its ethics code.

Analysis There's widespread anger in Europe about the reports that the US accessed personal data from leading internet companies, if the fiery debate at the European Parliament is anything to go by. Commissioner Tonio Borg said the EU wants a "clear commitment" from the US to respect the rights of European citizens when it comes to data protection. He said the commission would raise the issue with the US at a meeting in Dublin on Friday. The German MEP, Manfred Weber, said it was "completely unacceptable" that the US has different rules for its own citizens and those of other countries. A Dutch MEP, Sophie In't Veld, criticised the commission for failing to protect EU citizens. She said the reports of surveillance cast doubt on the special relationship between Europe and the US. But the British MEP Timothy Kirkhope warned against knee-jerk anti-Americanism, saying "friends listen most when you talk and not when you shout."

US officials say the snooping programme known as Prism, revealed in last week's leaks, is authorised under the Foreign Intelligence Surveillance Act (Fisa).

It gives the US National Security Agency (NSA) the power to obtain emails and phone records relating to non-US nationals.

But details about the individuals targeted under the act remain secret, and there are concerns the NSA is overstepping its powers.

Documents leaked to the Guardian and Washington Post newspapers claimed the US authorities had direct access to the servers of nine major US technology firms, including Apple, Facebook and Google.

Mr Snowden told the Guardian that individual operatives had the power to tap into anyone's emails at any time.

Although the firms have denied granting such access, saying they agreed only to legal requests, US officials have admitted Prism exists.

And on Tuesday, Republican Senator Lindsay Graham said US surveillance of phone records allowed the government to monitor phone records for a pattern of calls, even if those numbers had no known connection to terrorism.

Russia 'consider' asylum

One of the Guardian journalists who wrote the Prism stories, Glenn Greenwald, has promised "more significant revelations" to come.

In the US, the controversy has focused on the possibility that conversations of US citizens may inadvertently be captured.

But overseas, governments and activists point out that US law provides foreigners with no protection.

World media reaction The Liberation Daily in China has harsh words for President Obama: "Five years ago, Obama came to power waving an anti-George W Bush banner. Five years later, he is still exactly the same as George W Bush on invasion of privacy issues."

in China has harsh words for President Obama: "Five years ago, Obama came to power waving an anti-George W Bush banner. Five years later, he is still exactly the same as George W Bush on invasion of privacy issues." Russia's Izvestiya compares the revelations to a dystopian novel: "The frightening reality of the 21st Century is that the world has become a house with glass walls, notions of 'personal secrets' and 'confidential information' are turning into fiction before our very eyes."

compares the revelations to a dystopian novel: "The frightening reality of the 21st Century is that the world has become a house with glass walls, notions of 'personal secrets' and 'confidential information' are turning into fiction before our very eyes." India's Tribune is more forgiving: "The 9/11 terrorist attacks have changed the environment where cyber snooping is now defendable, even acceptable." World media fume

Justice Commissioner Reding tweeted: "This case shows why a clear legal framework for the protection of personal data is not a luxury but a necessity."

Mr Snowden is believed to be in hiding a day after he reportedly checked out of a Hong Kong hotel.

In the US, Mitch McConnell, the top Republican in the Senate, said the person responsible for the leak should be prosecuted to the fullest extent of the law.

He said privacy concerns were understandable, given the scope of the programmes, but added it was hard to comprehend why Mr Snowden would give information to US enemies.

Senator Dianne Feinstein, the chairwoman of the Senate intelligence committee, said the American authorities were "aggressively" pursuing him.

The California Democrat also accused Mr Snowden of "an act of treason".

The top Republican in the US House of Representatives, Speaker John Boehner, labelled Mr Snowden a "traitor".

In other developments on Tuesday: