Police in Spain, France and Paraguay have arrested around 14 people and liberated up to 15 women as part of a joint operation against sex trafficking.

Spanish police said in a statement Sunday they arrested nine people in the northern city of Pamplona on sex trafficking charges and liberated four exploited Paraguayan women.

They said the operation started after one of the victims dialed the Spanish help hotline against human trafficking back in 2015.

The operation was a joint effort with authorities in France and Paraguay, who also made arrests and freed women in simultaneous police bursts.

Among those detained in Pamplona are three of the alleged ring leaders of an international criminal organization based in Ciudad del Este near Paraguay's border with Brazil and Argentina.