ABUJA, Dec 17 (Reuters) - Gunmen in Nigeria released a Russian, a Mexican and a Nigerian who were kidnapped two weeks ago in the Niger Delta, a security source working in the industry said on Wednesday.

The three were taken hostage on Dec. 4 after their vessel Oceanic Orion was attacked some 13 nautical miles off the coast of Akwa Ibom state near a crude oil rig operated by Canada's Addax Petroleum <AXC.TO> <ACX.L>, the security source told Reuters, asking not to be named.

Piracy is common in the Gulf of Guinea off Nigeria's Atlantic coast while attacks on oil industry facilities and kidnappings for ransom are frequent in the creeks of the Niger Delta, home to Africa's biggest oil and gas industry.

The insecurity has cut Nigeria's oil output, which averages around 2 million barrels per day, by a fifth over the past three years. The country's installed production capacity is around 3 million bpd. (Reporting by Randy Fabi)

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