Philadelphia Mayor Michael Nutter ordered strict weekend curfews for the city's young people on Monday.
The curfews will come into effect on Friday.
"We will be prosecuting these young criminals to the fullest extent of the law," District Attorney Seth Williams said in a statement. "There is no excuse for what they did, and they have brought great shame upon themselves and their families."
The earliest curfew will take place in the neighborhoods of Center City and University City. All youths under the age of 18 must be home by 9 p.m.
Throughout the rest of the city, children under the age of 13 must be home by 10 p.m. and youths under the age of 18 must be home by midnight.
First-time offenders can be fined up to $300 while repeat offenders will be charged up to $500.
The curfew order follows a string of flash mobs and assaults throughout the city by young people. Recently, a group of approximately 40 youths assaulted two men in Center City.
Officials have pointed to social media as an easy way for volatile youth to assemble and act.
"What is making this unique today is the social media aspect," the city's deputy mayor for public safety, Everett Gillison, told the Associated Press.
Philadelphia officials have made it clear that they will do everything they possibly can to discontinue the dangerous flash mobs.
"We will apprehend you, prosecute you, and send you away," Williams said in the statement. "You will not damage the reputation of our great city."