Cotonou, Benin: Pirates have seized four crew members from a Greek-flagged ship off the coast of Togo while authorities in neighbouring Benin searched for nine people who were kidnapped from a Norwegian-flagged ship.

The incidents mark an escalation of pirate attacks in the Gulf of Guinea, which already is considered a high-risk area by the International Maritime Bureau.

The Greek Merchant Marine Ministry said four of the 24-member crew of the Elka Aristotle were kidnapped - one Greek, two from the Philippines and one from Georgia. The incident was confirmed by the ship's parent company, European Product Carriers.

The company said the remaining crew and the vessel were safe, adding it could not comment in detail but said "we are doing everything we can to ensure their prompt and safe release."