An oil tanker

A Greek-operated oil tanker seized off Togo was tracked down on Wednesday off the coast of Nigeria under the control of pirates, the ship's operator and Togolese authorities said.

The seizure early on Tuesday of the ship, which is operated by Golden Energy Management, underscored the growing risks to ships in the Gulf of Guinea, where piracy is rising but still not as common as off the coast of Somalia, reports Reuters.

"The vessel is presently sailing off the coast of Nigeria under the control of pirates who have the intention to steal the cargo," Golden Energy Management said in a statement.

The firm said they were in touch with a French naval ship that was nearby.

The crew are believed to be in good health and unharmed, the statement added. The Greek coastguard said there were 24 people on board, none of whom were Greek.

Colonel Inoussa Djibril, spokesman for the Togolese army chief of staff, confirmed the ship had been located on Wednesday morning in Nigerian waters with pirates onboard.

According to the International Maritime Bureau's website, there have been eight attacks and attempted attacks off the coast of Togo since January.