MSC has confirmed that its sub-Panamax container ship MSC Mandy has been attacked off the coast of Cotonou, Benin, with six crew members taken hostage.
The 2,700 TEU ship was under way in the Gulf of Guinea on Wednesday when the attack occurred.
Pirates boarded the vessel 55 nautical miles offshore, but the crew were able to secure the ship shortly afterwards.
According to MSC, the rest of the crew are safe and MSC Mandy has been diverted to an anchorage off Lagos, Nigeria.
The attack was first reported by the Maritime Domain Awareness for Trade - Gulf of Guinea (MDAT-GoG), a NATO partnership operated by the French and British navies.
MDAT-GoG collects daily voluntary reports from vessels under way in the Gulf of Guinea, an area with a high piracy risk.
Maritime piracy - particularly kidnapping - is a serious concern in the Gulf of Guinea with 100 seafarers kidnapped in 2017, according to Oceans Beyond Piracy and EOS Risk Group.
Another 35 have been reported in the first half of 2018.
Millions of dollars have been spent on additional maritime security measures for the region, but local authorities have had only limited success in foiling attacks.
The reach of Nigerian pirates has expanded from the historic centre of activity off the Niger River Delta to include waters off Benin and Ghana, well to the west.
Despite this expansion, most attacks are still concentrated in the vicinity of the petroleum hub of Bonny Island, with pirates searching out vessel targets as far as 100 nautical miles offshore.