Four women who had been trafficked through a network that coerced them through voodoo have been rescued. Authorities in Spain, the UK and Nigeria worked together to arrest 12 people to dismantle the Europe-wide human trafficking network.

The network used rituals including forcing the victims to eat raw chicken hearts while drinking whiskey and they also ripped out nails and hair to keep control over the women, Spanish police said.

Seven people were arrested in Cantabria, two in Vizcaya, two in Alicante and one in Manchester, UK.

Four women were rescued in Spain, police said, in an operation that saw collaboration between Spanish National Police, Europol, the UK's National Crime Agency, and Nigeria's National Agency for the Prohibition of Trafficking in Persons.

As well as Spain and the UK, the network was said to have operated in Italy, Niger and Libya as well.

Europol said that the operation had started a year earlier and that the victims were originally coerced by the network in Benin City, Nigeria.

Authorities said that the women were trafficked into Europe with fake documents where they were forced to work and live in squalid conditions while asylum applications were submitted in their names.

Spanish police said that the group used voodoo threats against the women and their families to gain control over the victims who were handed to madames to engage in prostitution.

The victims were forced to hand over money from the prostitution to pay for their transportation costs to Europe and for rent for the dorm-like housing they had to live in, authorities said.

Along with freeing the women and the arrests, Spanish authorities said that important documents and computer equipment relating to the investigation were recovered along with €975 in cash.