Men walk next to a car which was damaged during clashes between Saudi and foreign workers in Manfouha, southern Riyadh.

Men walk next to a car which was damaged during clashes between Saudi and foreign workers in Manfouha, southern Riyadh. Photo: Reuters

Saudi Arabia's sweeping crackdown on foreign workers has caused a severe labour shortage throughout the kingdom, with garbage reportedly piling up around major cities, crops going unpicked and school buses sitting idle without drivers.

More than 20,000 foreign workers have been arrested, after an amnesty that allowed those employed without proper visas to formalise their status ended last week.

Along with labour shortages and mass arrests there is also growing civil unrest, with violent clashes breaking out between workers and residents.

African workers sit on the roof of a police bus with their belongings before being transferred to a centre in the capital Riyadh ahead of their deportation.

African workers sit on the roof of a police bus with their belongings before being transferred to a centre in the capital Riyadh ahead of their deportation. Photo: AFP

"The crackdown on foreign workers has included raids on businesses and neighbourhoods as well as [the establishment] of police checkpoints," said Adam Coogle, a Middle East researcher for Human Rights Watch.

"If it continues at its current pace it has the potential to provoke more social unrest and potentially violence."

At least three people, believed to be Ethiopian workers, have been killed in clashes this week, the country's ambassador, Muhammed Hassan Kabiera, told Arab News.

Filipino illegal workers eat in their makeshift tent set up on a main street outside their consulate in the coastal seaport city of Jeddah.

Filipino illegal workers eat in their makeshift tent set up on a main street outside their consulate in the coastal seaport city of Jeddah. Photo: AFP

"We have been informed that so far about 23,000 Ethiopians have handed themselves in," Mr Kabiera said.

The crackdown targets workers who do not have valid residency or work permits, as well as those with valid documents who are not working for the employer designated in their formal papers, Mr Coogle said.

Almost one-third of Saudi Arabia's 28 million population are foreign workers employed in both skilled and unskilled professions.

But, Mr Coogle warns, workers have little control over their lives, with employers maintaining "inordinate power" over their them, dictating the validity of their residency and work permits, whether they can transfer to other jobs and, ultimately, whether they can leave the country.

Rather than targeting workers, the government should reform its inherently unfair employment system, Mr Coogle said.

In the past, Human Rights Watch and other groups have documented a wide range of abuses, including non-payment of salaries, forced confinement, food deprivation, excessive workloads and instances of severe psychological, physical, and sexual abuse.

Foreign workers are also blamed for so-called "morality crimes" such as drug use, prostitution and alcohol production and supply, said Dr Madawi Al-Rasheed, a visiting professor at the Middle East Centre at the London School of Economics and Political Science.

"Saudi society continues to entertain the illusion that it is pious, conservative and God-abiding and can only be corrupted by foreigners," she wrote on Thursday in the journal Al-Monitor.

"Many Saudis continue to wage war on Westernisation and modernity, blaming both on the presence of foreign elements, the media and globalisation."

The foreign worker is the embodiment of this outside invasion, she warned, and the reaction to them this week has been harsh.

The mistreatment of workers was so severe that in 2011 and 2012 countries providing much of the labour — including the Philippines, Indonesia, Nepal and Kenya — barred their citizens from migrating to Saudi Arabia for domestic work.

Only after the Saudi and Philippines governments signed a bilateral agreement to cooperate on labour issues, which included a $US400-a-month minimum wage, did the Philippines allow its citizens to resume work in Saudi Arabia, Human Rights Watch noted.

In its attempt to create more local employment to tackle an unemployment rate of more than 12per cent and lure more residents into the workforce, the government's crackdown on foreign workers has had unintended consequences.

About 40per cent of small construction firms have stopped work because their foreign workers couldn't get proper visas, Khalaf al-Otaibi, president of the World Federation of Trade, Industry and Economics in the Middle East, told Arab News.

And the state-backed Saudi Gazette reported that 20,000 schools are without janitors, while many bakeries, supermarkets, gas stations and cafes have been forced to close due to the labour shortages.