A day after a crowd of violent youths roamed through Center City and randomly attacked two men, the city's top enforcement officials decried the assaults and business leaders called for a stepped-up police presence.

"We will not tolerate marauding, destructive youth terrorizing our city," District Attorney Seth Williams said. "We will prosecute them to the fullest extent of the law, and we are working with the police to find ways to prevent these occurrences."

Four people, including an 11-year-old boy, who took part in the attacks face charges of assault and conspiracy.

They were among a crowd of young people who swarmed the sidewalk at Walnut and Juniper Streets about 9:15 p.m. Friday and pounced on a 33-year-old man, punching and kicking him. Police say the attack appeared to be random.

Moments later, at 15th and Sansom, a mob descended on a 59-year-old man and kicked and punched him. This attack, too, was random, police said.

Both men were treated at Thomas Jefferson University Hospital.

"It's just absolutely pitiful to have an 11-year-old running around Center City in a pack to do destruction," said Police Commissioner Charles H. Ramsey. "The mayor's upset; everybody's upset."

The beatings, which happened in plain view of people out for a stroll on a summer evening or on their way to popular Center City restaurants, stunned passersby. Calls to 911 flooded in to police, who quickly made arrests.

On Saturday, Raymond Gatling, 19, and three juveniles - ages 11, 16, and 17 - were charged with conspiracy, aggravated assault, and recklessly endangering another person. Gatling also was charged with robbery for taking a cellphone from the first victim.

Ramsey said he would meet with Mayor Nutter and District Attorney Williams to talk about how to prevent future assaults. He said they would work toward "a more coordinated response to put an end to this once and for all."

The commissioner said he hoped the courts would deal with the teens "in the harshest way possible."

He also faulted their parents. "At some point we have to hold the parents responsible," Ramsey said. "People have babies, they've got to take care of them.

"This is beyond stupid. One of those victims could have hit their head on the sidewalk and died. Then where would we be?"

Friday's rampage was the second in a month to hit Center City. In June, a group of about 100 teens beat, trampled, and robbed people after leaving a concert in North Philadelphia and roaming into Center City.

In response, police stepped up patrols in the area on Friday and Saturday nights.

Area business owners said that increased staffing seems to have waned.

"Something like this wouldn't have happened if there was more police presence," said Jeff Kile, bar manager of Good Dog Bar on 15th Street near Locust. "There's nothing I'd like to see more than a cop on every corner. It gets pretty hairy out there at night."

Paul R. Levy, president and chief executive officer of the Center City District, praised the Police Department for responding quickly and making arrests. But he, too, called for increased street patrols.

"Quite simply, the City of Philadelphia needs more police officers - both in the downtown and in the city's neighborhoods," he said.