(Reuters) - Nigerian police have arrested 37 people in southern Nigeria's Abia state on suspicion of being part of a major kidnapping ring, a spokesman said on Friday.

Nigeria is one of the world's highest rates of kidnapping, an enterprise that funnels hundreds of millions of dollars to the sophisticated criminal gangs that carry it out.

It is concentrated in the relatively prosperous south of Africa's biggest economy and top oil producer. The crime mostly targets Nigerians, although expatriates are sometimes snatched - kidnappers in Nigeria's Niger Delta region kidnapped three Dutch nationals on May 4, releasing them a week later.

"Police acting on a tipoff raided their den," police spokesman for Abia state Geoffrey Ogbonna told Reuters by text message. "We arrested 37 suspected kidnappers and they are still being screened as the investigation continues."

Nigeria