A Japanese whaling fleet left port Saturday under tight security, marking 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 northeastern fishing town of Ayukawa to cheers from local people, just weeks after the International Court of Justice (ICJ) slammed Japan's expedition in the Southern Ocean as a commercial activity masquerading as research.

The coastal hunt on Saturday was not part of Japan's annual Antarctic campaign and the ICJ ruling did not affect it.

But it holds symbolic importance as critics call for Japan to end the slaughter outright, and the hunt defied predictions that Tokyo would use the cover of the high-profile judgement to abandon a practice which the Japanese government has long defended as part of the island nation's heritage.

The ruling has left locals in Ayukawa -- among a handful of Japanese communities that depend on whaling -- worried about their livelihoods and the future of a town flattened by Japan's 2011 quake-tsunami disaster.

"People from outside are saying a lot of things, but we want them to understand our perspective," said Koji Kato, a 22-year-old crew member, before leaving on the hunt.

"For me, whaling is more attractive than any other job."

At around 10:30 am (0130 GMT), whistles sounded as the flotilla accompanied by a trio of coastguard patrol boats set off following a ceremony attended by about 100 people.

Supporters shouted "hold on, hold on" to the departing mariners, who expected to catch about 50 whales during the hunt which will last until early June. Another campaign farther out in the Pacific, also unaffected by the ICJ ruling, is expected to start within a couple of months.

"Japan lost the court case. But we say that the ruling has nothing to do with coastal and offshore whaling in the northwest Pacific," Yoshiichi Shimomichi, an official with the Association for Community-Based Whaling, told the crowd.

- 'A rough road' -

Japan has hunted whales under a loophole in the 1986 global moratorium which allowed lethal research on the mammals, but Tokyo has made no secret of the fact that their meat ends up in restaurants and fish markets.

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 still planned to go to the icy waters to carry out "non-lethal research", it has said, raising the prospect that harpoon ships would return the following year.

That would put Japan on a collision course with anti-whaling nations like Australia, which hauled it before the international court, arguing that Tokyo's Antarctic hunt was skirting a commercial whaling ban.

Once a key source of fuel and food, Japan's consumption of whale meat has considerably diminished in recent decades and is no longer a regular part of most people's diet.

However, powerful lobbying forces have ensured the continued subsidisation of the hunt with taxpayer money.

Tokyo has always maintained it was trying to prove whale populations were big enough to sustain commercial hunts.

Despite global condemnation, there were no protesters at Saturday's event -- unlike the Antarctic hunt which has seen violent clashes between whaling crews and activists.

Earlier this year, the town of Taiji attracted international headlines over an annual dolphin slaughter -- made infamous in the 2009 documentary "The Cove" -- as activists tried to film the gory scene to the dismay of wary locals.

"It's been a rough road," said Kazutaka Sangen, the mayor of Taiji who attended Saturday's event.

"The Japanese government said it would accept the court judgement, but we are not happy. We have done serious research and no one acknowledges that," he told AFP.

- 'Nothing else here' -

Ayukawa, which claims a whaling industry dating back to the early 20th century, still bears the scars of the 2011 disaster, with gnarled bridge railings and empty lots where buildings once stood.

As the town struggles to rebuild, Ryo Watanabe, 53, a fisheries co-operative association official, wondered why all the fuss about whaling.

"This is not something special -- it's part of our daily life," he said.

For Masayoshi Takahashi, a retired whale processing factory worker, the future was grim.

"Without whaling, this town is done," the 71-year-old said.

"What will the fishermen do? Seaweed harvesting season is only one or two months a year. There is nothing else here."