Serbian police have arrested eight people suspected of smuggling migrants from the border with Bulgaria to the European Union.

Serbian Interior Minister Nebojsa Stefanovic says the "criminal group" arrested Wednesday is suspected of smuggling more than 200 migrants for a fee of 250 euros ($270) each "over a long period of time."

Police say that seven Serbs and one Afghan citizen have been arrested. Two additional suspects are on the run.

Thousands of migrants have been stuck in Serbia after its EU neighbors Hungary and Croatia shut their borders to prevent their entry in March 2016.

Many of the migrants arriving in Serbia have turned to people smugglers to try cross into the EU illegally.