Nigeria caused a stir in the sector by closing out the tankers amid limited explanation, with owner’s association Intertanko leading the protests and noting some of the ships locked out had never visited the country.

Noah Parquette, JP Morgan’s shipping analyst, said: “Regardless, if the ban holds we believe this could have a positive effect on the tanker market, as the ban would artificially reduce local supply off West Africa and decrease trading efficiencies, effectively lowering the overall supply potential of the fleet.”

Nordic American Tankers, New York's Overseas Shipholding Group and Gener8 Maritime, Greece's Maran Tankers Management, Russia's SCF Group, John Fredriksen's Frontline and Belgium's Euronav are among the major owners with vessels on the Nigerian list.

"Intertanko protests in the strongest possible way that these bans should be lifted with immediate effect until grounds and evidence for the ban have been given to each vessel and vessel owner/operator, and the owner/operator has had an opportunity to respond," wrote general counsel Michele White in a letter addressed to Gbenga Komolafe, the general manager of NNPC's oil marketing division last week.