Image caption There are an estimated nine million migrant workers in Saudi Arabia

Saudi Arabia is rounding up thousands of illegal migrant workers, after an amnesty introducing new employment rules expired.

Nearly a million Bangladeshis, Indians, Filipinos, Nepalis, Pakistanis and Yemenis are estimated to have left the country in the last three months.

Four million others obtained work permits before Sunday's deadline.

Some 3,000 Indonesian illegal workers in Jeddah are in detention, awaiting deportation, Indonesian officials say.

They had gathered under a flyover with all their belongings, giving themselves up to the authorities.

An estimated nine million migrant workers in Saudi Arabia - more than half the workforce - fill manual, clerical, and service jobs.

Saudi Arabia has the Arab world's largest economy, but the authorities are trying to reduce the 12% unemployment rate among native Saudis.

The government is carrying out its threat that if any illegal migrants are left they will be punished by fines, prison or deportation.

Companies that break the new rules will also face penalties.

Human Rights Watch has denounced the country's labour system as "abusive".

"The kafala, or sponsorship system ties migrant workers' residency permits to sponsoring employers, whose written consent is required for workers to change employers or leave the country," it has said.

"Employers often abuse this power in violation of Saudi law to confiscate passports, withhold wages and force migrants to work against their will or on exploitative terms."