“We are doing everything we can from our embassy in Ghana to resolve the situation,” said a spokesman for the Spanish foreign ministry, which confirmed that five of the crew were Spanish citizens.

Pirates boarded and hijacked the tanker, taking her 23 crew hostage, in the early hours of Wednesday, according to the International Maritime Bureau.

The coast of Benin, which neighbours Nigeria, Africa’s largest oil producer, has seen a steep increase in hijackings this year, with 19 ships coming under attack.