Stores in a usually bustling district of the Saudi capital were closed, construction work at some sites slowed and bakeries around the country shuttered Tuesday, amid a clampdown on illegal workers.
On Monday, authorities began arresting people who had failed to take advantage of a months-long grace period to leave or legalise their status, and detentions were continuing on Tuesday.
Residents in Riyadh said stores were closed in the popular Al-Batha commercial hub, a cheap market that employs low-paid Asian vendors.
At the same time, residents said work had slowed at a construction site in Thumamama, north of Riyadh.
And Fahd Al-Salman, chairman of the National Committee for Bakeries at the Council of Saudi Chambers, told the Arab News daily that the labour shortage had led to the closure of many bakeries in the kingdom.
Meanwhile, private schools that had closed on Monday re-opened following reassurances that expat teachers, working illegally, could remain until the end of the first school semester in December, residents said.
Nearly 4,000 people have so far been arrested in Jeddah alone, the kingdom's commercial capital, said local police spokesman Lieutenant Nawaf al-Bouq.
In the capital Riyadh, 818 illegal immigrants, including two women, were arrested on Tuesday, the police spokesman there General Nasser al-Qahtani told AFP.
In the southwestern Jazan province, border guards have arrested more than 8,000 people of various nationalities trying to cross the border to Yemen in the past 24 hours, the official SPA news agency quoted a spokesman there as saying Tuesday.
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Three thousand of these have been deported as authorities are still finalising deportation procedures for the remainder, the spokesman said.
Hundreds of expatriates have also been arrested in other areas across the kingdom, according to local media.
Nearly a million Bangladeshis, Filipinos, Indians, Nepalis, Pakistanis and Yemenis, among others, took advantage of the amnesty announced on April 3 and then extended for four months, and have left the country.
Another roughly four million have legalised their situation by finding employers to sponsor them, a must to reside in most Gulf monarchies.
On Monday, illegal Indonesian workers staged a protest in the port city to protest their consulate's slow pace in handling administrative procedures needed to organise their departure, local press reported.
In the past, foreigners desperate to work in the country were willing to pay for sponsorship, and sponsoring expatriates became a lucrative business for some Saudis.
But under the new rules, workers may be employed only by their own sponsors, banning the practise of working independently or for non-sponsors.
Saudi Arabia, the world's largest oil exporter, is seen as a goldmine for millions of people from Asia and elsewhere in the Arab world, who find work as common labourers, drivers, porters and house maids.
Expatriates account for around nine million of the country's 27-million-population.
Saudi Arabia has the Arab world's largest economy, but the unemployment rate among natives is above 12.5 percent, a figure the government is aiming to reduce.