"Some 18,413 more expatriates are waiting for deportation from state-run temporary shelters to their countries," the spokesman for the Saudi Passport Department, Ahmed al-Luhaidan said, according to the Saudi daily newspaper al-Riyadh.

Saudi authorities started in November a nationwide clampdown against immigrants after the end of a seven-month grace period given to them to legalize their status or leave.

The government says the campaign is ultimately aimed at providing jobs for Saudis, as the official unemployment in the country stands at 12 per cent.

Most of an estimated 8 million expatriates in Saudi Arabia, the world's top oil exporter, come from India, Bangladesh, the Philippines, Ethiopia, Yemen and Egypt.

Hundreds of thousands of workers have already left the kingdom amid tougher conditions for migrants.

Earlier in November, Saudi police have killed three Ethiopian migrant workers in the latest round of violence against the foreign immigrants in the kingdom.

The clashes broke out on Tuesday in the impoverished Manfuhah neighborhood of the capital Riyadh, where thousands of African workers, mostly Ethiopians, were waiting for buses to take them to deportation centers.

Foreign workers cannot change jobs or leave Saudi Arabia without the permission of their sponsors, who are often Saudi companies or individuals who provide workers to businesses for profit.

Most of the sponsors confiscate the passports of the workers for the duration of their contract.

Human rights groups have criticized Saudi Arabia over the condition of migrant workers in the kingdom and called on Riyadh to change sponsorship system for migrant workers.

NJF/NJF