The Japanese whaling fleet, carrying armed Coast Guard officers, was on the move on Friday, local news reports said.
The factory ship Nisshin Maru, two harpoon ships, and another that has acted as security vessel for the fleet were heading out in Japan's Inland Sea, according to Kyodo news.
Already the whalers are weeks behind their usual departure time for the Antarctic.
In recent weeks the Nisshin Maru made several short forays from port following a refit for what are believed to have been sea trials.
"With the Coast Guard on board and the all vessels underway it appears that they are finally leaving," said Paul Watson, leader of the Sea Shepherd conservation group.
Mr Watson said he did not expect the whalers to each the Antarctic until 21 January at the earliest.
His group has four ships to meet the fleet, but has been restrained by a United States court from attacking the whalers.
with AFP
