Six members of the crew of a Danish oil tanker attacked by pirates last weekend in the Gulf of Guinea have been kidnapped, the French navy announced Friday, after the ship was found and rescued off the coast of Sao Tome e Principe.

The Mongasa Reformer, which flies the flag of Liberia, was attacked on Saturday evening by a pirate boat when it was 140 nautical miles from the Congolese port of Pointe-Noire, and contact with its crew was lost shortly thereafter.

The French Defense Ministry said in a statement that the ship was spotted Thursday "in the early afternoon" by a drone launched from a French patrol boat deployed by Paris as part of its "Courimp" mission to combat piracy in the region.

As for the pirate boat, which was spotted near the tanker during the first sortie, its trace disappeared during a second sortie of the drone.

When the French boat approached the tanker a few hours later, its crew reported on the radio that "six of its own have been taken by pirates."

Of the 10 crew still aboard the Mongasa Reformer, three received minor injuries and are being treated by a military doctor.

The company, "Mongasa", announced in the morning that part of the crew had been kidnapped, but it did not specify the number of those kidnapped.

The nationalities of the kidnapped sailors are still unknown, but media in the Scandinavian country said they were not Danish.

AFP contacted the company, which is based in Fredericia, Denmark, but did not want to give details.

"We are thinking of the abducted crew members and their families at this difficult time," the company said in a statement. "We are working closely with local authorities" to secure the sailors' return.

No damage was recorded on the ship or its cargo of fuel, according to the statement.

The 135-meter-long vessel was attacked on Saturday night, but the owner company did not announce the attack until Tuesday, three days after losing contact with the crew.

Some of the crew were able to report that they had taken shelter in a "compartment in the ship" before communication was lost. Since then, it has launched searches in the eastern Gulf of Guinea.

According to Congolese authorities contacted by AFP on Tuesday, the attack was carried out by three men.

According to the Franco-British "Maritime Domain Awareness for Trade Golf of Guinea" mission, the attack was carried out by five pirates.

The Gulf of Guinea represents an important sea passage for hydrocarbon-rich countries, extending 5,700 km between Senegal and Angola, and has been witnessing piracy activities for several years.

Recently, however, the attacks have decreased thanks to the joint efforts of the coastal states and European countries.

Denmark, the main commercial maritime power through its giant Maersk, sent a frigate in the fall of 2021.

In 2022, about two dozen incidents were recorded in the Gulf of Guinea, according to the Maritime Informatics Cooperation and Awareness Center. In 2021, 52 accidents were recorded, and 115 in 2020, according to the Maritime Security Experts Agency, based in Brest, France.

Since the beginning of the year, two attacks have been reported in the region, according to the International Maritime Bureau (IMB).

The Danish Shipowners' Association said Tuesday that the tanker's case proves that "piracy problems off the coast of West Africa are still far from being resolved".

The Maritime Trade Organization is concerned about the rise in attacks again as Western militaries focus their attention on Europe due to the war in Ukraine.

Most of the attacks in recent years have been carried out by Nigerian pirates by speedboats.

Some of them captured large fishing vessels, which they use as bases from which they launch their speed boats to launch attacks far from the coast.