Kenyan domestic workers in Saudi Arabia endure imprisonment, racism and sometimes rape with working conditions so abusive that they often amount to "forced labour and human trafficking," Amnesty International said in a report on Tuesday.
The report was released as US President Donald Trump was scheduled to arrive in Riyadh for an official visit.
The rights NGO detailed the brutal conditions faced by more than 70 women who worked as domestic workers in Saudi Arabia.
They "faced awful living conditions and inhumane treatment including sexual, verbal and physical assault", the report said.
"Employers typically confiscated their passports and phones and sometimes withheld their wages."
Amnesty said the Kenyan government was complicit in the exploitation.
"The Kenyan government is actively encouraging labour migration, and the Saudi Arabian authorities claim that they have introduced labour rights reforms," said Irungu Houghton, executive director of Amnesty International Kenya.
"Yet behind closed doors domestic workers continue to face shocking levels of racism, abuse and exploitation," he added.
The average monthly salary was 900 Saudi riyals ($240) with no overtime, Amnesty found, amounting to an hourly rate of 50 cents.
"I have no freedoms, because once you are inside you never go out. You don't go out and do not see out. This made me feel like it's a prison," said one of those interviewed.
Many were deprived of food, and had to sleep in inadequate conditions like a store cupboard or the floor of a child's bedroom.
Several women reported incidents of sexual violence, including a woman who described being raped five times by the husband.
Amnesty described "systemic racism" in the attitudes towards Kenyans, often called "animal" and "monkey" by members of the household.
There are roughly four million domestic workers in Saudi Arabia, all of them from foreign countries, including 150,000 from Kenya, according to labour market statistics cited by Amnesty.
The traditional "kafala" sponsorship system binds migrant workers to their employer. There have been some reforms to the system in recent years, Amnesty said, but "tight restrictions" remain.
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The NGO said it had received no response to queries sent to the Saudi and Kenyan authorities.
AFP was also unable to obtain a comment from the Kenyan government, which encourages labour migration to help its struggling economy.