MILWAUKEE – 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.

“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 alleged attack, which authorities say took place Monday in a house. A 40-year-old man said in court papers to have confessed to having 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,” prosecutor Matthew Torbenson said Thursday.

Numerous violent crimes have shocked this Midwestern city this summer, starting with a weekend in late May 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. Torbenson 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.

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.