Pirates have seized an oil tanker and its crew near the coast of Nigeria, the third hijacking in the Gulf of Guinea in two weeks.

Nigerian naval officials say pirates seized the Singapore-flagged ship Abu Dhabi Star near the Lagos port. There are conflicting reports about whether the vessel was in Nigerian waters when pirates took control.

Authorities say they believe the pirates will sail the ship to another vessel to siphon out the oil.

Last week pirates seized an oil tanker anchored in Togo's port, an area where crews typically feel more protected from pirate attacks.

The director of the International Maritime Bureau, Pottengal Mukundan, says Togo's navy was unable to rescue that tanker.

“This is very disturbing because it sends the wrong signal to these criminals, that they can succeed in these attacks,” he says.

Pirates freed the tanker and crew seized last week after stealing the oil on the vessel.

Hijackers in the Gulf of Guinea typically release ships and crew members after stealing cargo, unlike pirates in Somalia who usually hold the crew for ransom.

Mukundan warned attacks in the Gulf of Guinea will likely rise unless governments do more to catch and punish the pirates.