The seven suspects -- three Serbs, three Ukrainians, and a woman from Moldova -- are members of what the police called an "international organized criminal group."
Police said the suspects published advertisements in Ukraine and Moldova about jobs in Western Europe to lure girls into leaving their countries.
The women were transferred through Romania, and their documents taken away.
The suspects were arrested in Belgrade.
The Balkans is one of Europe's major human trafficking routes.
(AP, dpa)