Tokyo: The first dolphins of the season have been slaughtered in the small Japanese town of Taiji, campaigners say, starting an annual cull highlighted in the Oscar-winning documentary The Cove and repeatedly condemned by animal rights groups.

Activists from the environmentalist group Sea Shepherd have been monitoring a bay in Taiji, southwestern Japan, since the six-month dolphin hunting season began earlier this month.

Fisherman corral dolphins during last season's hunt in Taiji, Japan. Credit:Reuters

"First pod of 2014-2015 being driven into cove now," the activists from Sea Shepherd, who call themselves "Cove Guardians", posted on Twitter at 10.33am local time.

About an hour later, @CoveGuardians on Twitter said: "First dolphin murder of the drive hunt season is complete as dead bodies are dragged to Taiji butcherhouse."