The streets of the Saudi capital Riyadh were unusually quiet on Monday as many expatriates stayed at home to avoid the start of a government crackdown on illegal foreign workers.

Building sites were deserted, Riyadh’s stuttering rush-hour traffic flowed smoothly and many shops and market stalls were closed in normally busy neighbourhoods that are home to large numbers of Saudi Arabia’s lower-income foreign community.

The government of the world’s top oil exporter has promised raids on businesses, markets and residential areas to catch expatriates whose visas are invalid because they are not working for the company that ‘sponsored’ their entry into the kingdom.

In the Riyadh Industrial Zone, where many workers are foreigners, most shops were closed on Monday morning, according to a witness who said he saw a dozen people scurry for cover when they heard a police siren from a nearby road.

“Nobody has come to buy anything at all today. It’s a very bad situation,” said Abu Safwat, a Syrian who owns a machine parts shop in the area.

The enforcement of visa rules is another effort to end a black market for cheap imported workers, cut the foreign labour force and free up private-sector jobs for Saudi nationals.

“The field security campaign, in coordination with the Labour Ministry, will take place in all cities, provinces, villages and rural towns,” Interior Ministry spokesman Major-General Mansour Turki said in a statement on Sunday.

The official Saudi unemployment rate of 12 percent excludes a large number of citizens who say they are not seeking a job.

Raising private sector employment in a country where most Saudis are in government jobs, and where businesses employ more foreigners than locals, is a major challenge for the kingdom.

About nine million foreigners, mostly unskilled labourers or domestic workers, live alongside 18 million Saudis. The money they send home is vital for their own nations, such as Yemen, Ethiopia, the Philippines, Indonesia, India, Pakistan and Egypt.