Prosecutors in Southern California charged a Saudi Arabian princess on Wednesday with human trafficking and accused her of bringing a Kenyan woman to the US and holding her against her will as a servant.

The accused woman, Meshael Alayban, 42, brought the Kenyan to the US in May and paid her $220 a month while holding her passport and keeping her confined to an apartment complex in Irvine, California, where Alayban lived, Orange County prosecutors said in a statement.

The servant, whose name was not released, had to wash dishes, cook, clean, do laundry and iron without a day off, prosecutors said.

Authorities said they found four Filipino women in the Irvine home who also may have had their passports seized by Alayban's family, and an investigation is under way into whether others were involved in the alleged human trafficking scheme.

Police arrested Alayban early on Wednesday at her apartment, a day after the Kenyan woman escaped and flagged down a bus driver, the statement said. Alayban is charged with one felony count of human trafficking.

"The laws of our nation and California do not tolerate people who deprive or violate the liberty of another and obtain forced labour or services," Orange County district attorney Tony Rackauckas said in a statement.

The only occasion when the Kenyan woman was allowed to leave the Irvine apartment complex was when she carried the bags of Alayban's family during an outing, prosecutors said.

The Kenyan also attended to other people linked to Alayban who lived in the same complex, according to the statement.

Alayban had first hired the Kenyan woman as a domestic servant in March 2012 in Saudi Arabia in her family's palace, prosecutors said. She is accused of holding the woman's passport then as well and forcing her to work every day for 16 hours.

Orange County prosecutors said the Kenyan woman originally came to work for Alayban by signing a two-year contract with an employment agency that promised her $1,600 a month to labour for eight hours a day, five days a week.

Irvine police chief David Maggard Jr said in a statement that his officers were "gratified to have been able to help" the Kenyan woman "find her freedom."

Alayban's attorney, Paul Meyer, said in an email that "the complaints were about hours worked and wages paid."

"We intend to fully investigate this matter, and expect that the truth will resolve it," he said.

Alayban appeared in court in Orange County on Wednesday and a judge set her bail at $5 million. She remains in custody at a women's jail, according to a website for the Orange County Sheriff's Department.

Prosecutors have expressed concern Alayban could try to flee if released on bail, and the judge ordered her to wear a GPS device and stay in Orange County if she is let out.

Alayban faces up to 12 years in prison if convicted. - Reuters