Britain is considering disrupting online social networking such as Blackberry Messenger and Twitter during civil unrest, Prime Minister David Cameron said on Thursday, a move widely condemned as repressive when used by other countries.
Egyptian authorities shut down mobile and Internet services in January during mass protests against then-President Hosni Mubarak, while China is quick to shut down online communication it sees as subversive.
Police and politicians have said online social networks, in particular Research in Motion's popular Blackberry Messager (BBM), were used by rioters and looters to coordinate during four days of disorder across England this week.
"We are working with police, the intelligence services and industry to look at whether it would be right to stop people communicating via these websites and services when we know they are plotting violence, disorder and criminality," Cameron told parliament during an emergency session prompted by the riots.
Many of the rioters favoured Canadian firm RIM's BBM over Twitter and other social media because its messages are encrypted and private.
The company said on Monday that it cooperates with all telecommunications, law enforcement and regulatory authorities, but it declined to say whether it would hand over chat logs or user details to police.
RIM's encrypted services have been blamed for aiding militant attacks in India and for allowing unrelated men and women to communicate in Saudi Arabia and the United Arab Emirates.
In August last year, a source close to talks between RIM and Saudi authorities said the company had agreed to hand over information that would allow monitoring of BBM.
Online social media was also widely used by members of the British public in recent days to help others avoid troublespots and to coordinate a clean up after the rioting had ended.
BBM has more than 45 million active users worldwide, 70 percent of whom use it daily, sending billions of messages, pictures and other files in total every month.
Authorities grappling with violent unrest should avoid heavy-handed clampdowns on social media and instead try to enlist the help of the public against the rioters, said John Bassett, a former senior official at British signals intelligence agency GCHQ and now a senior fellow at the Royal United Services Institute.
"The use of social media in the unrest looks like a game-changer. But any attempt to exert state control over social media looks likely to fail," he told Reuters.
"A much better approach would be to encourage and support individuals and community groups in identifying alarming developments on social media and even speaking out on the internet against extremists and criminals, and ensuring that the police have the skills and technical support to get pre-emptive and operational intelligence from social media when necessary."
(Additional reporting by Peter Apps; editing by Matt Falloon and Gareth Jones)