MOSCOW, February 12 (RIA Novosti) – Moscow police detained more than 5,000 illegal migrants during checks on the city’s subway system in 2013, which led to more than 500 deportations, the Interior Ministry said Wednesday.

Police began a sweeping crackdown on illegal migration last year, including a series of raids on markets and other workplaces.

A police spokesman said in September that the subway stings were aimed at decriminalizing Moscow’s metro by identifying and suppressing crime committed by migrants.

Rights groups have complained, however, that such sweeps leave foreigners open to extortion and abuse at the hands of corrupt police officers.

Moscow metro police chief has said that up to 80 percent of all robberies and assaults in the subway system are committed by migrants, mainly from Central Asia and Russia’s North Caucasus regions. City authorities claim the subway attracts criminals who pick pockets and peddle forged documents, drugs and even weapons.

Mayor Sergei Sobyanin says crime in Moscow is on the downswing, having dropped by more than 15 percent in 2013 on the previous year.