Hundreds of Sea Shepherd activists are heading for the Faroe Islands for an unprecedented campaign against a traditional dolphin hunt that they call "an obsolete massacre," the conservation group said Friday.

Relays of volunteers will patrol the ocean and beaches of the remote North Atlantic archipelago, an autonomous country within Denmark, from mid-June to October to try to block the killing of pilot whales, members of the dolphin family, in a practice known locally as a "grind".

"This is a tradition that's hundreds of years old, dating from when inhabitants needed to eat dolphins to survive," Sea Shepherd director Alex Cornelissen told AFP in Amsterdam, en route for a ferry to the Faroe Islands, which lie between Iceland and Scotland and have a population of around 50,000.

"But the subsistence argument is no longer valid, this is now more entertainment than anything, an obsolete massacre," he said, noting that the dolphins are in any case unfit for human consumption as they contain high levels of mercury.

The timing of the "massacre" depends on when the cetaceans are spotted offshore, and Sea Shepherd activists have intervened in the Faroes several times in the past.

The mammals are then forced into a bay by flotillas of small boats before being hacked to death with hooks and knives -- a "grind" that many locals defend as a cultural right.

- 'Barbaric events' -

The activists are ready for confrontation and to go to prison if needed, they said.

They have no authorisation for the campaign, which will involve several small boats, a large ship and several land vehicles.

The activists will stand guard "to sound the alarm, interfere, and document" what happens, according to a Sea Shepherd statement.

"We will be prepared to defend ourselves if necessary. If a grind occurs, we will thoroughly document and broadcast the barbaric events. The world will be watching and we will show the truth of the slaughter," the conservation group said.

"We have to spot the dolphins before the hunters and drive them as far as possible away from the coast," said Lamya Essemlali, in charge of the Grindstop 2014 campaign.

"If a group of dolphins is spotted before we can drive them away then we'll have to use other methods, notably on land," she said.

Relations between the activists and Faroe inhabitants are usually good tempered, the activists said, but not always.

"Some of our cars there have been vandalised and covered in dolphin blood," said Cornelissen.

Since records began, more than 265,000 small cetaceans have been killed in the Faroe Islands, mainly between the months of June and October, according to Sea Shepherd -- some 1,500 since July last year.

Whaling in the Faroes stretches back to the earliest Norse settlements more than 1,000 years ago, and community-organised hunts date to at least the 16th century.

The International Union for the Conservation of Nature (IUCN) Red List of Threatened Species does not list the status of the pilot whale for a lack of data.

"During our last campaign in 2011 no dolphin was killed," said Essemlali.

"But as soon as we left the Faroe Islands, having been there a month and a half, the grinds started again."