Pirates attacked a Norwegian vessel off the coast of Nigeria on Thursday and kidnapped nine Nigerian nationals onboard, the ship’s Norwegian owner BW Offshore said.

The Sendje Berge, an offshore support vessel for the oil and gas industry, came under attack at 0320 GMT, BW Offshore said in a filing to the Oslo stock exchange.

There has been no news on the nine Nigerians since they were taken, but nobody remaining on board the ship had been hurt, according to the statement.

At the time of the attack, the Sendje Berge was working at the Okwori oilfield on behalf of China’s Addax Petroleum.

The Gulf of Guinea, which includes the Nigerian coast, has in recent years been the scene of a growing number of attacks by pirates who loot ships or kidnap crews or passengers for ransom.