Officials said a months-long investigation into the ring led to the arrests of four Spanish and 14 Nigerian suspects, the Spanish version of The Local reported.
The police said in a statement the organization also had associates in Nigeria who selected those they considered vulnerable.
Police said the gang lured Nigerian women by promising them a better life in Spain. Before flying them to Europe, the gang members allegedly forced the women to swear their loyalty by having them eat a raw chicken heart during a witchcraft ceremony, The Local said.
The women would be in debt for the travel costs and work-related paperwork the gang supposedly underwritten, The Local said.
Debts ranged from about $52,000 to $77,000, police said, meaning the women entered prostitution in several industrial estates as soon as they arrived in Malaga, the capital of Malaga province in Spain's Autonomous Community of Andalusia.