ST. PAUL — Prosecutors in Minnesota charged four suspects Wednesday in an alleged sex-trafficking ring that targeted women who are Chinese nationals and kept them isolated.

The ring operated out of Irvine, California, but involved criminal activity in North Dakota and Minnesota, mainly in the eastern Twin Cities area, Washington County Attorney Pete Orput said.

“It seemed to me that this was the Uber of sex-trafficking,” Orput said at a news conference announcing the charges. “You can order up a human being. They target women who don’t speak English, who constantly move so they can’t develop ties.”

The suspects — a man and three women — have been arrested and face felony charges in Washington County that include sex trafficking, promoting prostitution and concealing criminal proceeds.

The only Minnesotan charged in the case is Dongzhou Jiang, 28, of Blaine. Orput said he acted as a regional boss, taking the women to various sites around the Twin Cities where they were forced to have sex with men.

Three Irvine, California, residents were charged in the case: Hong Jing, 48; Sophia Wang Navas, 49; and Fangyao Wu, 23. Wu is Jing’s daughter. Authorities believe the three California women, all awaiting extradition to Minnesota, made up the “operational control center” of the ring.

Jiang’s attorney, Tyler Bliss, told The Associated Press he had no comment. Online court records do not list attorneys who could comment for the other defendants.

The alleged ring was connected to thousands of advertisements for sexual services placed on the website Backpage.com in 29 states over the past two years, prosecutors said. Authorities identified at least six victims between the ages of 32 and 49, but said there could be more.

The women were forced to work 12 to 14 hours a day and had to pay house fees, transportation costs and hotel expenses as well as provide their own food, prosecutors alleged.

Ramsey County Attorney John Choi called it the most sophisticated trafficking operation he has seen, and praised the cooperation among investigating agencies.

“These victims were especially vulnerable, as they were trapped in a foreign country where they barely spoke the language and sold for sex,” Choi said in a statement. “Today marks significant progress in our statewide efforts to combat human trafficking.”