Police have arrested around 300 people in raids at three illegal migrant camps. Most of those detained had no documents.
The camps were inhabited by nationals of Armenia, Belarus, Ukraine and Russia.
Two of the camps were located inside disused factories, while the third stretched along a railway in the west of Moscow.
The migrants were preparing pizzas and sushi for sale, officials say, in violation of health and safety regulations.
In one of the camps, the police found spare parts for luxury makes of cars, including Lamborghini, Mercedes and BMW. They also found several cars ready to be resprayed. The police are now checking whether the cars were stolen.
Back in April 2011, policemen in the capital found a whole underground community living below the city.
More than 100 immigrants from Asian countries were residing in a bomb shelter equipped with the basics for life, including showers and toilets – and even a mosque.
The shelter belonged to a factory that used to produce military equipment. Access to such places is usually strictly prohibited to foreigners.