An 11-year-old girl was sexually assaulted by as many as 20 boys as a 16-year-old girl watched and told her what sex acts to perform, authorities say in the latest mob attack to rock Milwaukee and set off another round of civic soul-searching.

"It almost leaves me speechless. It is just senseless acts of violence. It is inhumane. It is embarrassing to the city of Milwaukee and its people. ... There should be outrage," Barbara Nuell-Moore, director of the neighborhood-improvement group Project Respect.

The 16-year-old girl and a 15-year-old boy have been charged in juvenile court in the attack, which took place on Monday in a house on the city's north side. A 40-year-old man who also had sex with the child may also be charged, authorities said.

As for the others, "we're dealing with a lot of nicknames so we're trying to track down these people," said prosecutor Matthew Torbeson.

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Numerous violent crimes have shocked the city this summer, starting with a Memorial Day weekend in which 28 people were shot. Homicides overall are down this year, but two other categories of violent crime are up from 2005 — assaults by 22 percent and robberies by 36 percent, Police Chief Nan Hegerty told the Milwaukee Journal Sentinel.

Hegerty's spokeswoman said the chief had no comment on the alleged gang rape.

According to court papers, the 11-year-old girl told police she was interested romantically in the 16-year-old girl, who looked and dressed like a boy.

The alleged victim and two friends went to the 16-year-old's house, where the child performed oral sex on three teenage boys, according to court papers. The 40-year-old uncle of the 16-year-old admitted he also had sex with the 11-year-old and told police that the 16-year-old was directing the child, the papers said.

The 11-year-old then went to the basement, where there were about 15 males and she told police she "began to choose who she wanted to perform oral sex on," court papers said.

The 16-year-old told police that the 11-year-old had told her she wanted to perform oral sex on the boys in the house. The 16-year-old denied encouraging her.

The 16-year-old girl and the 15-year-old boy were charged with being a party to sexual assault. Torbeson said he will probably seek to have them tried as adults.

Several mob attacks have taken place in Milwaukee's inner city in recent years. In 2002, more than a dozen people, mostly boys, chased a man through the streets and beat him to death with shovel handles, rakes and tree limbs.

A mentally ill man died after being beaten and robbed by a group in 2004. Four days after that attack, a 14-year-old boy was kicked, punched and hit on the head with a piece of lumber after he exchanged words with a girl. He was in a coma for two weeks. Also that summer, four brothers were beaten by a group armed with bats, bottles, sticks and socks stuffed with canned food.

On Thursday, Alderman Mike McGee Jr. walked through the neighborhood where the alleged sexual assault happened and talked to residents. He later declared there is a crisis in the city's neighborhoods.

"We have to have the community held responsible, parents held responsible. That's the bottom line," he said.

Willie Brown, 26, who lives in the area, said Thursday that neighbors are outraged.

"If all those brains couldn't get together and figure out that was a baby?" he said, adding he has a 3-year-old daughter. "I don't have no respect or no love for people who do that." He added: "Whatever they get, they got it coming."