Updated

Serbian police say they have arrested five suspected people smugglers and found 170 migrants as part of an international effort to curb the illegal transfer of migrants toward Western Europe.

The police said Wednesday the 36-hour operation spread over several European and Balkan countries and resulted in a total of 39 arrests and the discovery of 580 migrants.

Countries dealing with Europe's migrant crisis have increased cooperation to stop the flow of migrants after more than a million people entered Europe in 2015. People smuggling has been on the rise since Balkan countries closed their borders to migrants in March.

Serbian police say the joint action included police from Austria, Bulgaria, Croatia, Macedonia, Germany, Hungary, Romania, Serbia, Slovenia, Switzerland and Europol.