In a strong message to those who incite violence on social networks, a British court sentenced two men to four years in prison for using Facebook to try to organize a riot. It's the sternest punishment yet for abuse of social networks during the UK riots.

In Chester Crown Court south of Liverpool, 20-year-old Jordan Blackshaw of Marston near Northwich, and Perry Sutcliffe-Keenan, 22, of Warrington, were sentenced for creating Facebook events calling for violence.

No one repsnded to the calls, but Blackshaw was charged on 9 August and Sutcliffe-Keenan was charged on 10 August.

Prime Minister David Cameron last Thursday called for an inquiry into whether the government should restrict social media sites that are being used to plan violence. Rioting across London and in several othercities saw lives lost, buildings burned and shops looted, causing millions of pounds in losses and damages.

Residents last week called to warn of the Facebook events plotted by the two men, which caused the police to arrest them, said Jane Gregory, spokeswoman for the Cheshire Police. Both men pleaded guilty to offenses under the Serious Crime Act of 2007.

"We took a large amount of calls and had direct contact to our own social media page from very, very worried residents," Gregory said. "From that, we did some investigations and arrested them."

Blackshaw publicised an event called "Smash Down Northwich Town," targeted at an area southeast of Liverpool. Sutcliffe-Keenan created a Facebook page called "Let's Have a Riot in Latchford," which is near Warrington east of Liverpool, police said.