Authorities are clamping down on teenagers terrorising the US city of Philadelphia.
The mayor announced a 9pm curfew for youths under 18 after flash-mobs, often organised through social media sites, carried out a wave of random attacks.
Seventy-five people have been arrested for violating the newly enforced curfew.
Al Jazeera's John Terrett reports from Philadelphia.
Source: Al Jazeera