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LAGOS, Oct 10 (Reuters) - Two oil workers kidnapped by gunmen in Nigeria, a Colombian and a Filipino, were released overnight in good health after 12 days in captivity, authorities said on Wednesday.

The two men were seized by gunmen disguised as soldiers from an oil industry construction yard on Sept. 27 in Port Harcourt, the largest city in Nigeria's southern oil-producing Niger Delta. A Colombian colleague was shot dead during the abduction.

Esteban Conejos, Philippine foreign affairs undersecretary for migrant affairs, said the Filipino electrician was freed at about midnight.

"He's now back in his company and undergoing a medical check-up. We'll have to ask him if he wants to go back to his family in the Philippines or stay there," Conejos said.

A security source said both men, contractors for Italian oil services company Saipem, were in good health.

Kidnapping of foreign workers is common in the Niger Delta, where militants complaining of poverty and neglect have crippled Africa's largest oil industry.

But the line between militancy and crime is blurred and most abductions are motivated by the prospect of a ransom.

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