Saudi Arabia vowed "zero tolerance" against the illegal employment of migrants, more than a year after tens of thousands of foreigners were deported in an earlier crackdown.
The labour and interior ministries "confirm that the inspection campaigns aim to track violators of labour and residency", the official Saudi Press Agency (SPA) said.
"Violations will be met with zero tolerance," it said, targeting those who allow the illegal employment of foreigners.
Companies whose staff are not properly registered, or who work for others, can be fined up to USD 27,000 and face other penalties including jail and deportation of the manager.
Individual violators, including religious pilgrims who overstay, will also be tracked down, SPA said.
"They will be caught at their residences. Procedures will be implemented to penalise and deport them," it said.
In 2013, Saudi Arabia said it deported more than 60,000 illegal foreign workers after a months-long amnesty to formalise their status or leave the kingdom.
Nearly a million migrants from various countries took advantage of the amnesty to leave voluntarily.
Another four million were able to find employers to sponsor them, a legal requirement in Saudi Arabia as in several other Gulf states.
Ethiopia said it repatriated more than 100,000 of its citizens following the crackdown, while official media in Sudan said in excess of 11,000 workers had returned voluntarily when the amnesty ended.
Millions of migrant workers in Saudi Arabia do everything from manual labour to management, but the government has been trying to boost employment of Saudi nationals.
At the end of 2012, official data said there were about 20 million Saudis out of a total population of around 29 million in the kingdom, the world's biggest oil exporter.
Saudi unemployment was around 12 percent in the first half of last year, according to official data cited by Jadwa Investment.
