LONDON - BlackBerry said on Thursday it would work with mobile operators to switch off its popular messenger service if they were ordered by authorities to do so during civil unrest, after police singled out the system as a key tool used in last month's riots.

Appearing before politicians investigating the large-scale disorder that swept Britain in early August, executive Stephen Bates of Blackberry-owner Research in Motion said the company would comply with orders given in special circumstances such as threats of terrorism or mass criminality.

"From our perspective we comply with the law and if the instruction ... would be to close down the mobile networks which is the method by which that would be enacted, we would then comply, we would then work with those mobile operators to help them meet the obligations as defined by that act," Bates said.

Police and parliamentarians said at the time of the unrest that social media, in particular Blackberry Messenger (BBM), had been used by rioters and looters to incite and coordinate violence.

BBM appears to have been preferred over Twitter and other social media sites because its messages are encrypted and private.  

Speaking when police were still grappling with nights of violence in London and other major English cities, Prime Minister David Cameron said Britain could consider disrupting online social networking during civil unrest.  

Since then however, the government has said it was unlikely it would go that far, after the home secretary, Theresa May, met police and executives from RIM, Twitter and Facebook.  

Bates said the company had a strong view that communications and social media were a force for good and it didn't see it "being a good way forward" to suspend social networks during periods of large-scale disorder.

Alexander Macgillivray, responsible for public policy at Twitter, told the committee it would be an "absolutely horrible idea" to do so, and quoted police as saying they used it for good during times of crisis.

Richard Allan, director of policy in Europe at Facebook, said social media allowed families and friends to know they were safe.

RIM has previously said it cooperates with local law enforcement and regulatory officials, but it has declined to say whether it would hand over chat logs or user details to police.