China's official army newspaper Sunday branded the United States Internet surveillance programme exposed by former spy Edward Snowden as "frightening", and accused the US of being a "habitual offender" when it comes to network monitoring.

The People's Liberation Army (PLA) Daily hit out at the US for implying that spying on citizens from other countries was justified, and said that the PRISM monitoring programme had probably been used to collect large amounts of data unrelated to anti-terrorism operations.

The remarks about the programme are some of the most scathing to appear in China's state-run press following Beijing's refusal to make an official comment.

"US intelligence agencies are 'habitual offenders' with regards to network monitoring and espionage," the article, attributed to the PLA's Foreign Languages Institute, said.

"There is reason to believe US intelligence agencies, while collecting anti-terrorism information online have also 'incidentally' collected a lot of information in other fields."

Under the so-called PRISM programme, the US National Security Agency can issue directives to Internet firms like Google or Facebook to gain access to emails, online chats, pictures, files and videos that have been uploaded by foreign users.

"US President Obama has said that PRISM is not directed at US citizens," the article said.

"The implication is that for the purposes of US security, monitoring citizens of other countries is not a problem. This simple, overbearing logic is the frightening aspect of the PRISM programme.

"The US government says that PRISM is an anti-terrorism program, and does not involve any other matters. But anyone with intelligence expertise can tell this is "admitting ones guilt by protesting innocence."

China has stayed tight lipped following the revelations from the former US government subcontractor, which included claims of US hacking directed at China and which came amid tensions between Washington and Beijing about online espionage.

On Thursday the foreign ministry gave little insight into Beijing's thinking.

"I have no information to offer," ministry spokeswoman Hua Chunying told a regular briefing.

Snowden, who is in hiding in Hong Kong, has vowed to fight any attempt by the US to extradite him.

Protesters rally in Hong Kong to support Snowden
Hong Kong, Hong Kong (AFP) June 15, 2013 - Hundreds of protesters staged a rally in rain-hit Hong Kong Saturday to urge the city's government not to extradite former spy Edward Snowden, and slam the United States for its surveillance programmes.

Snowden, 29, has gone to ground in the city after blowing the lid on the US's vast electronic surveillance operation and has vowed to fight any extradition request.

The city's first major demonstration on the issue saw protesters, including pro-democracy lawmakers, activists and a large number of expatriates march to the US consulate holding banners and shouting "Defend Free Speech", "Protect Snowden", "No Extradition" and "Respect Hong Kong Law".

Many blew their whistles loudly and wore masks with Snowden's face on it.

"Today we all blow the whistle," shouted Tom Grundy, a British blogger and activist who lives in Hong Kong.

One protester held a sign of US President Barack Obama's famous 'Hope' poster, edited to show the leader as a spy wearing large headphones. Another sign read: "Betray Snowden, Betray freedom".

The US has launched a criminal investigation after Snowden, a former CIA technical assistant, leaked details of Washington's secret Internet and telephone surveillance programmes.

The protesters, made up of 27 civil society organisations, handed a letter over to the US consulate addressed to Consul General Steve Young, which said: "For many years, the US State Department has publicly supported the cause of Internet freedom and criticised other governments for conducting cyber attacks, surveillance and censorship.

"We now understand, through recent revelations, that the US government has been operating their own blanket surveillance systems and allegedly conducting cyber warfare against Hong Kong.

"This is a violation of Human Rights of people of Hong Kong and around the world."

Snowden told the South China Morning Post newspaper earlier this week that there have been more than 61,000 NSA hacking operations globally, targeting powerful "network backbones" that can yield access to hundreds of thousands of individual computers.

There were hundreds of targets in mainland China and Hong Kong, Snowden was quoted as saying.

Hong Kong has a long-standing extradition treaty with the US, but Beijing has the potential to veto any ruling.

"We are going to see a lot of political juggling between two of the biggest powers in the world in order to possibly extradite Mr. Snowden," lawmaker and Hong Kong entrepreneur Charles Mok told protesters.

"Who is losing? You and I, all the Internet users in the world. Why? Because we in Hong Kong know the best, we live outside of the Great Firewall of China," Mok said.

And the rally comes amid increasing concern in the city over perceived mainland interference.

Rally spokeswoman Oiwan Lam told AFP: "Snowden is now in Hong Kong and falls under our jurisdiction and we have to defend the fact that the city's courts are in the position to deal with the situation."

Maverick Hong Kong lawmaker "Long Hair" Leung Kwok-hung meanwhile called US President Obama and his Chinese counterpart Xi Jinping "twin brothers" when it comes to Internet spying.

"The most important thing is in defending Mr Snowden. If he can be extradited and be punished, who will be the second whistleblower?" he told protesters.

"There are a lot of Mr. Snowdens all over the world. It's like an execution if they grab Mr. Snowden and extradite him," Leung told AFP.

"They will condemn him to hell in a small cell for tens of years," he said.

Following the rally, the city's chief executive Leung Chun-ying said in a statement: "The Hong Kong...government will handle the case of Mr. Snowden in accordance with the laws and established procedures.

"Meanwhile, the government will follow up on any incidents related to the privacy or other rights of the institutions or people in Hong Kong being violated," the statement added.

So far the United States has not filed a formal extradition request to Hong Kong, a former British colony that retained its separate legal system when it returned to Chinese rule in 1997.

Beijing ultimately retains control over defence and foreign affairs but it and Hong Kong's governments have yet to make any comment about Snowden's case.