Nigeria ? Gunmen armed with dynamite assaulted a Chevron Corp. tanker in Nigeria’s southern oil-producing region early Tuesday, killing a Nigerian sailor and kidnapping an American oil worker and five other foreigners, authorities said.

The restive region’s main militant group, the Movement for the Emancipation of the Niger Delta, claimed responsibility for the attack.

Navy Capt. Obiora Medani said the sailor was a guard aboard the tanker FPSO Oloibiri, which was in waters off Bayelsa state.

Chevron said it shut down a station pumping oil to the ship, cutting its daily production by 15,000 barrels.

Tope Idowu, a spokesman for the California-based company, said the gunmen kidnapped an American, four Italians and one Croatian. He said the American worked for Chevron in Nigeria while the rest were employees of a subsidiary, Chevron Shipping Co.

No demands had been made by the attackers, Idowu added.