Police in Italy have arrested 11 Nigerians for allegedly trafficking young women and girls from Nigeria to exploit them as sex slaves.

Police Officer Antonio Salvago in the southern Italian city of Catania said Monday that the victims underwent a voodoo rite to bind them to their debts after they promised to pay up to 40,000 euros ($43,000) for a journey they thought would bring them to a better life in Europe.

Salvago says the rite made them obey their smugglers and pimps.

The victims, all under age 25 and some as young as 16, traveled through Libya before crossing the Mediterranean by boat with thousands of other migrants.

Catania Chief Prosecutor Carmelo Zuccaro says the investigation shows that illegal immigration breeds more serious crimes of exploitation and forced prostitution.