Two people have been arrested for scanning police radios during the G20 protests in Pittsburgh and using Twitter to advise protesters on police movements.

Elliot M. Madison and Michael Wallschlaeger were arrested in a hotel room that the police describe as filled with computers. Officers allege that Madison and Wallschlaeger were scanning police radios to direct protesters away from law enforcement officials.

The FBI arrested the pair and seized computers, mobile phones, MP3 players, anarchist literature and pictures of Vladimir Lenin and Karl Marx. They also found 11 gas masks, five pairs of goggles, a slingshot, four arm pads, eight facemasks and a collection of test tubes, droppers, beakers and a mortar and pestle.

Madison, a self-described anarchist, runs a legal centre known as The People's Law Collective for those arrested in the course of protests, and the two men also produce a radio show entitled This week in radical history.

About 5,000 protestors visited the G20 meeting of world economic leaders in Pittsburgh, of whom 190 were arrested. Police deployed tear gas and sonic weapons in an attempt to control protesters, but have been criticised for being heavy handed.