Kidnappers in Nigeria have released four foreign oil workers who were held hostage for more than three weeks.

Mediators handed the British, Pakistani, French and Dutch citizens over to security officials in the oil city of Port Harcourt on Saturday.

The four had been kidnapped June first by gunmen dressed as police from a Port Harcourt residential compound used by a U.S. oil services firm Schlumberger Limited.

Kidnapping has become commonplace in Nigeria's southern Niger Delta, with more than 100 foreigners taken captive this year. The hostages are generally released unharmed after a ransom is paid.

Some of the abductions are the work of criminal gangs seeking ransom, while others have been carried out by militants demanding that local villages get more of the region's oil wealth.

Residents in the Niger Delta are largely impoverished despite the billions of dollars the government and oil companies reap from oil production.

NIgerian President Umaru Yar'Adua has sought to ease tensions in the region since his inauguration last month.


Some information for this report was provided by AFP, AP and Reuters.