The mayor called the moves part of a "holistic response" to the flash mob phenonenom that has plagued the city the past two summers.
In the most recent incident on July 29, teens beat random strangers in Center City. Among the four young males arrested in those attacks was an 11-year-old boy.
"We are not joking around. This not a game. This is not fun," Nutter thundered. "It is no one's idea of how to spend time in any part of the city."
But the mayor attempted to balance his palpable anger at what he called "erratic, senseless attacks," with a focus on "positive options for our young people."
"When we ignore our young people's needs, when we don't offer job opportunities, when we don't invest in their education or in their future, all of us have failed them," he said.
The announcements came a day after Nutter delivered an impassioned and personal speech from the pulpit of Mount Carmel Baptist, his church of 25 years. The mayor blistered absent fathers and neglectful parents in the black community, and told troublemaking teens, "You have damaged your own race."
"I said what needed to be said, at a time that it needed to be said. And I think, quite honestly, people were ready to hear it," Nutter said Monday.
The mayor was backed at Monday's news conference by a huge contingent of city officials and leaders from the black community, including J. Whyatt Mondesire, the leader of the Philadelphia NAACP.
Mondesire said the mayor's Mount Carmel speech "took courage" to deliver, and said he supported Nutter's efforts to rein in the flash mobs.
"These are mostly African-American youths and they need to be called on it," he said. "Right now, our overwhelming concern is the safety of all Philadelphians."
The boundaries where the new curfew will apply in Center City are Vine Street to Bainbridge Street, and from the Delaware River to the Schuylkill River.
In University City, the curfew will apply from Market Street to Baltimore Avenue, and from 38th to 43rd Streets.
"If we have problems come up in other parts of the city, we'll move the grid," said police Commissioner Charles H. Ramsey. "But right now these are the areas . . . where we think we can have the greatest impact."
The previous curfew for minors between 13 and 17 had been 10:30 p.m. during the week, and midnight on Friday and Saturday. This past weekend, police cited a dozen teens for violating the old curfew, Nutter said.
Teens can be fined up to $300 and parents can face fines up to $500 after a child violates curfew for a second time. Nutter said he would work with City Council in the fall to write a comprehensive new curfew law.
Nutter said the early curfew does not mean police will arrest any teen out after those hours.
"But, if you are out wrecking havoc, if you are out causing problems, if you are out doing things you shouldn't be doing, we're going to get you off the streets," he said.
City officials promised to continue seeking harsh punishment against teens arrested for participating in the assaults and vandalism that have come to mark the flash mobs.
"When all else fails and people give up all the norms of society, they're going to deal with us," said District Attorney Seth Williams. "There will be no diversionary programs, no community service, for people who commit random acts of violence."
Nutter repeated another familiar refrain - that flash mobs are not "just a policing problem. This is challenge for all of us as community members."
He called for community leaders and volunteers to step up to help youths, but he also issued another scolding to parents.
"It is your responsiblity to know where your kids are, what they are doing and who they are with," he said. "They are your children. You need to raise them."
The city is going to continue reaching out to teens through youth-friendly media and a number of other initiatives are under consideration, said Jordan Harris, the executive director of the city's Youth Commission.
"If we're going to tell them what they can't do, we have to tell them what they can do," he said.
Radio personalities and North Philadelphia natives Izzo and DJ Damage also plan to discuss flash mobs and encourage positive outlets for teens on their shows on 100.3 The Beat.
DJ Damage said he plans to speak to student at 15 high school this coming school year.
"That's really the pledge I'm taking for the city," he said. "I support the mayor 100 percent."
Nutter said the stakes were high - flash mobs bruise the reputation and vitality of the city - and he made no apologies for saying that black teens who participate in them are harming their race.
"When (people) see that kind of behavior and activity it is in fact damaging to all African-Americans and all Philadelphians," Nutter said. "That's why I said what I said."
Contact staff writer Troy Graham at 215-854-2730, firstname.lastname@example.org or @troyjgraham on Twitter.
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