Japanese whaling vessels left port Friday bound for the Southern Ocean on their annual hunt of the marine mammals, a media report and Greenpeace said.
Citing the Fisheries Agency, Kyodo News reported three vessels had departed from the far-western port of Shimonoseki, while environmental group Greenpeace said the mother ship had left another port also in the country's west.
"The mother ship, Nisshin Maru, left Innoshima today," said Greenpeace Japan's executive director Junichi Sato.
"Today was virtually the last day when they could leave for the Antarctic Sea," he said, adding that the fisheries agency had announced that the departure would take place within this month.
The mother ship would join the three vessels that left Shimonoseki earlier in the day, Kyodo said.
The fleet plans to hunt up to 935 Antarctic minke whales and up to 50 fin whales through March, the fisheries agency said earlier.
Japanese authorities refused to confirm either departure to AFP.
"We do not disclose when the vessels leave or left for safety reasons," said an agency official said.