MOSCOW, August 7 (RIA Novosti) – Moscow police carried out yet more raids targeting migrants and marketplaces Wednesday, detaining hundreds of people.

A special sweep operation involving some 400 police officers took place at the Sadovod market, a sprawling area in southeastern Moscow trading a variety of goods that employs many migrants. Over 1,000 people have been held there as of Wednesday morning, the police reported, but did not say on what grounds they were detained.

The operation is part of the city’s recent drive to “decriminalize” Moscow with checks of market places and other sites which house and employ many migrant workers.

The city’s law enforcement authorities detained thousands of people in a string of raids, launched last week, following an attack on a police officer who was seriously injured at a Moscow market when attacked by an angry mob as he was trying to arrest a rape suspect.

Late Tuesday, police opened a criminal case against six people over alleged use of slave labor connected to the illegal migration of over 700 people including Vietnamese nationals, officials said in a statement.

The illegal migrants were kept as slave workers at sites controlled by the group, where they lived and worked making garments in poor conditions. The suspects had taken away their travel documents and kept them locked up, the police said.

Meanwhile, at least seven people were detained Tuesday on suspicion of organizing illegal migration from Uzbekistan and Kyrgyzstan to Russia, officials said, according to Russian media reports.

Russia has the world’s largest number of illegal migrants, accounting for almost seven percent of the country’s working population, according to an International Migration Outlook report issued last year by the Paris-based Organization for Economic Cooperation and Development (OECD).