The Sea Shepherd conservation group has intercepted a Japanese harpoon fleet with the help of a drone on Christmas Day.

A Sea Shepherd Conservation Society spokesman confirmed to AAP it had caught up with the fleet at 37 degrees south, 1600km above Antarctic waters.

A military-style drone was used to intercept the fleet.

"This is going to be a long, hard pursuit from here to the coast of Antarctica," Captain Paul Watson said.

"But thanks to these drones, we now have an advantage we have never had before - eyes in the sky.