UPDATE 1-Oil vessel, nine crew released in Nigeria -company

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PARIS, Jan 7 (Reuters) - French oil services firm Bourbon (GPBN.PA) said on Wednesday nine crew members were released unharmed in Nigeria along with their hijacked vessel, which had been captured by unknown gunmen in speedboats on Sunday.

Bourbon did not say how it obtained the release of the vessel, the Bourbon Leda, and its crew -- five Nigerians, two Ghanaians, one Cameroonian and one Indonesian.

Piracy and kidnappings for ransom are common in Nigeria's oil producing Niger Delta.

"Bourbon announces that the Bourbon Leda vessel and its nine crew members, captured off the coast of Nigeria in the night of Saturday to Sunday, have been freed. All nine crew members are in good health," the company said in a statement.

Bourbon thanked Nigerian authorities for their help but gave no details of the terms of the men's release.

The Bourbon Leda, a fast supply intervention vessel, was seized off Bonny Island, in the Niger Delta, where a major crude export terminal and a liquefied natural gas plant are located.

Security sources in Nigeria had said the vessel was on its way to a Royal Dutch Shell (RDSa.L) offshore oilfield at the time of the attack.

The Niger Delta, a vast network of mangrove creeks opening into the Gulf of Guinea, is home to Africa's biggest oil and gas industry but supplies have been crippled by a wave of attacks that began in early 2006.