Three ships, led by the 720-tonne Yushin Maru, set sail from Shimonoseki in western Japan on a mission officially said to be for “scientific research”, according to local media reports.
The government’s fishery agency declined to confirm the reports, citing security reasons.
In February, Japan cut short its hunt for the 2010-2011 season by one month after bagging only one fifth of its planned catch, blaming interference from the US-based environmental group Sea Shepherd.
The fleet aims to catch around 900 minke and fin whales this season, according to a plan submitted by the government to the International Whaling Commission.
Commercial whaling is banned under an international treaty but Japan uses a loophole to carry out “lethal research” on the creatures in the name of science.
It makes no secret of the fact that whale meat from this research ends up on dinner tables and in restaurants.