No details were provided on the number of crew kidnapped, nor their nationalities the owner said there was no reported damage to the vessel or cargo.

Pirates who seized a Danish oil tanker off Congo last week have abandoned the ship and taken some crew members with them, while the rest were found in good health, the ship's owner said on Friday.

The Danish-owned Liberian-flagged Monjasa Reformer disappeared after pirates boarded it over the weekend.

The ship was 140 nautical miles off the coast of Congo and had 16 crew members on board; it's not clear how many have been taken by the pirates.

The French navy found the ship on Thursday.

The rescued crew members are all in good health and safely located in a secure environment," the ship's owners, Monjasa, said in a statement.

No details were provided on the number of crew kidnapped, nor their nationalities.

"Our thoughts are with the crew members still missing and their families during this stressful period," Monjasa said, adding that it was "working closely with the local authorities" to obtain the sailors safe return.

The owner said there was no reported damage to the vessel or cargo.

The shipowner said the crew had initially notified the company that manages the vessel that pirates had boarded and that the entire crew was safe in the tanker's secure room or "citadel", "in accordance with the onboard anti-piracy emergency protocol".

It said communications were then lost.

The Liberian-flagged vessel was "sitting idle" at the time of the incident.

The Gulf of Guinea, stretching from Senegal to Angola, has long been plagued by piracy.

But in recent years, navies of West African countries, particularly Nigeria, and international navies, including the Danish, stepped up patrols in the region.

It contributed to a steady decline in incidents recorded by the IMB Piracy Reporting Centre.

Last year there were only 19 incidents reported compared to the 35 attacks in 2021 and 84 attacks in 2020.

The shipowners' organization Danish Shipping has, however, called for more action to be taken.

"The current situation clearly shows that most countries in the region do not have the necessary resources or capabilities to respond to such an incident," it said in a statement released earlier this week.

"We should therefore also consider what smaller contributions to increased training or surveillance Denmark can send while our naval vessels are occupied elsewhere," it said.