Five Russian oil workers kidnapped from their vessel off Nigeria's Niger Delta last week have been released unharmed, a senior state security official said on Monday.
More than 200 foreigners have been abducted in the region where crime and militancy surged until 2007 when there was a lull. Most have been released in exchange for money.
Below is a chronology of some major kidnappings in Nigeria's oil delta in 2008.
March 4, 2008 - A German employee of German-Nigerian construction group Julius Berger, an arm of Bilfinger Berger AG, was kidnapped between the Rumuji and Emuoha areas of Port Harcourt. He was released around 12 hours later.
-- May 23 - Two foreign employees of oil services company Lonestar, one from Pakistan and one from Malta, were kidnapped at Omoku in the Niger Delta. They were released on June 26.
-- June 3 - Gunmen kidnapped two Lebanese employees of Setraco, a local engineering company, near the town of Amassoma.
-- June 19 - The Movement for the Emancipation of the Niger Delta (MEND) rebels claimed responsibility for an attack on Royal Dutch Shell's Bonga oilfield off the coast of Nigeria. The rebels warned of further attacks and kidnapped Jack Stone, the U.S. captain of a nearby supply ship. He was later released.
-- June 26 - One Portuguese and one Ukrainian national among 11 crew members taken on May 13 from an oil supply vessel contracted to U.S. oil firm Chevron, were released.
-- July 11 - Two Germans, employees of construction firm Julius Berger, Nigerian unit of Germany's Bilfinger Berger, were kidnapped at Emohua in Rivers state. A soldier was killed in the kidnapping. On July 20 the company announced it was pulling out of the Delta.
-- July 24 - Gunmen take 11 Russians and a Ukrainian in an attack on a vessel off Bonny Island. Some were released the next day. The last five were released on Monday.
-- July 25 - Gunmen in speedboats kidnapped two oil engineers, one from the Philippines and one Nigerian, in Port Harcourt. They were employed by Damas Oil and Marine Services. Another Filipino was seized while buying food on land.
-- July 26 - Eight Russian, Latvian and Lithuanian men were seized from a liquefied petroleum gas (LPG) tanker off the mouth of the Bonny river in the Niger delta. They were released late on the same day.
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(Writing by David Cutler, London Editorial Reference Unit;