Meshael Alayban, 42, is accused of forcing a Kenyan woman to work 16 hours a day while paying her far less than what she was originally promised. Alayban was arrested on Wednesday.

Authorities say Alayban took the woman's passport, precluding her escape. Her lawyer called the case a dispute over work hours.

In November, California voters toughened human trafficking penalties.

If convicted, Alayban faces a maximum sentence of 12 years in prison, double the punishment prescribed before voters approved the law known as Proposition 35.

Prosecutors say she is one of six wives of Prince Abdulrahman bin Nasser bin Abdulaziz al-Saud, a scion of the Saudi royal family.

The unnamed Kenyan woman had begun working for Ms Alayban last year in Saudi Arabia under a two-year contract with an employment agency.

That contract guaranteed her $1,600 (£1,050) a month for eight-hour work days, five days a week, California officials said. Instead she was paid $220 a month and forced to work twice as long, according to prosecutors.

The 30-year-old Kenyan woman also alleges her passport was taken from her when she arrived in Saudi Arabia. It was only returned to her long enough for her to travel to the US with Alayban.

In California, she said she was forced to perform household chores for at least eight people in four units at the same block of flats where she was allegedly held captive. When she managed to escape, she flagged down a bus driver and later went to police.

NTJ/BA