In the Saudi capital Riyadh, hundreds of foreign workers were piled into buses to be taken to deportation centres on Wednesday evening.
The Saudi authorities have been rounding up undocumented immigrants, most of them from African countries, since an amnesty period ended on November 4.
The clampdown is aimed at reducing the size of the black market in cheap foreign labour and creating more jobs for Saudis.
Tensions have flared since the police raids began as soon as the amnesty ended.
The authorities say that three Saudis and two foreigners have been killed in clashes.
But those resisting are in the minority. More than 23,000 Ethiopians have reportedly handed themselves in. At least 30,000 Yemenis are said to have left in the last two weeks.
Before the crackdown began, nine million foreigners were estimated to be working in Saudi Arabia – making up a third of the population.
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