Six crew members who were kidnapped by pirates from a Danish oil tanker off the coast of Congo last month have been rescued from Nigeria, the ship’s owner announced on Monday.

The Liberian-flagged Monjasa Reformer had 16 sailors on board when it was attacked on 25 March. Despite being owned by a Danish company, none of the crew members were Danish.

When the French navy found the 443-feet tanker the following week off the coast of Sao Tome and Principe in the Gulf of Guinea, the remaining crew said six of their colleagues had been kidnapped.

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Monjasa has not revealed whether ransom was paid for the release of the crew members.

Monjasa CEO Anders Ostergaard said that the rescued crew members were in relatively good health, considering the difficult circumstances they had been under for more than five weeks.

They have undergone medical checks and are being repatriated to their home countries to reunite with their families.

Pirates have long been a risk in the Gulf of Guinea, a major shipping route stretching 5,700 kilometres from Senegal to Angola, with Nigerian gangs carrying out most of the attacks.

However, since 2021, pirates have been raiding farther out in international waters. Their violence and sophisticated tactics have prompted shippers to call for a more robust foreign naval presence to curb attacks, as was done to combat Somali pirates a decade ago.

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Many of the recent attacks have been carried out by Nigerian criminal gangs using speed boats from hideouts in the Delta region. Some gangs have captured larger fishing vessels which they use as a “mothership” base to raid further out to sea.