Two Japanese whaling ships and a surveillance vessel are reported to have left for the annual whale hunt in the Antarctic.
The Japanese news agency Kyoto News says the three ships departed from the western port of Shimonoseki on Saturday to join other ships in hunting up to 935 Antarctic minke whales and up to 50 fin whales up until March.
It says the country's fisheries agency had kept the departure date secret as a precaution against obstruction by militant anti-whaling groups such as Sea Shepherd.
Japan's whale hunts have long drawn criticism from activists and foreign governments, AFP reports, but Tokyo defends the practice, saying eating whale is part of Japanese culinary tradition. It says research is required to prove that whale populations can sustain commercial whaling.
Activists say this "research whaling" is a cover for commercial whaling, which is banned under an international agreement.
Japanese whalers and Sea Shepherd activists have routinely clashed violently in exchanges in the Southern Ocean.
The catch fell to a record low of 103 Antarctic minke whales last season, a drop attributed to the anti-whaling group's campaign.