A Japanese whaling fleet has left port under tight security in the first hunt since the UN's top court last month ordered Tokyo to stop killing whales in the Antarctic.

Four ships departed from the fishing town of Ayukawa in the northeast, marking this season's start to a coastal whaling program not covered by the International Court of Justice's landmark ruling - which found Japan's Southern Ocean expedition was a commercial activity masquerading as research.

Some observers had predicted the Japanese government would use the cover of last month's court ruling to abandon what many have long considered the facade of a scientific hunt.

But Tokyo's decision to continue whaling was likely to set off a new battle with critics who had hoped the ruling would bring an end to a slaughter that the Japanese government has embraced as part of the island nation's cultural heritage.

Some Japanese politicians have derided criticism from abroad as little more than cultural imperialism by the West, while locals in Ayukawa expressed fears the court's decision could ultimately ruin their livelihoods.

About 10:30 am local time, whistles sounded as the flotilla, accompanied by a trio of coastguard patrol boats, set off after a ceremony attended by about 100 local dignitaries and crew.

There were, however, no protesters among the crowd - a far cry from the Antarctic hunt which saw sometimes violent clashes between Japanese whaling crews and activists trying to end the hunt.

The town on Japan's northeast coast was ravaged by Japan's 2011 tsunami and still bears the scars of the disaster. Local people say their small community's existence rests heavily on the hunt.

"No matter what the court ruling was, all we can do is let everyone see that we're still hanging in there," said Koji Kato, a 22-year-old crew member.

"People from outside are saying a lot of things, but we want them to understand our perspective as much as possible. For me, whaling is more attractive than any other job."

Yuki Inomata, works in a local whale meat processing factory, said he was "glad" that the annual hunt got under way despite questions about the future of the industry in Japan.

"I don't know what will happen next but I hope we can continue whaling," said Inomata.

Tokyo called off the 2014-15 season for its Antarctic hunt, and said it would redesign the controversial whaling mission in a bid to make it more scientific.

But vessels would still go to the icy waters to carry out "non-lethal research", raising the possibility that harpoon ships would return the following year.

That would put Japan on a collision course with anti-whaling nations like Australia, which brought the case to the international court, arguing that Tokyo's research was aimed at skirting a ban on commercial whaling.

Japan has hunted whales under a loophole in a 1986 global moratorium that allowed it to conduct lethal research on the mammals, but has openly admitted that their meat made its way onto menus.