PORT HARCOURT, March 21 (Reuters) - Fire tore through a Nigerian navy base in the restive Niger Delta on Friday, killing at least two sailors and destroying four vessels, authorities said.

"There was an electrical explosion this morning at about 09:00 (0800 GMT) at the Nigerian Navy Pathfinder jetty. It was purely an accident," said Sagir Musa, army spokesman in Port Harcourt, the Delta's main city.

"Two naval men died in the explosion," he said, adding that around three boats and a barge had been destroyed.

One private security contractor involved in the oil industry said five Nigerian sailors had been killed. He said four bodies had been found and that divers were searching for a fifth.

The Delta, home to Africa's biggest oil industry which exports around 2.1 million barrels per day, is frequently hit by abductions of oil workers for ransom, armed robberies and crude oil smuggling.

Unknown gunmen aboard a speedboat killed a Nigerian sailor on Wednesday when they attacked a security vessel as it travelled to the Delta port of Onne, used to supply oil industry contractors, security sources working in the oil sector said. (For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/ ) (Reporting by Austin Ekeinde; Writing by Nick Tattersall)

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