Fishing communities in Japan are alarmed over the decision to release contaminated water stored at the wrecked Fukushima Daiichi nuclear plant, a move that has also set off a diplomatic ruckus with neighbours China and South Korea.

Japan's government said on Tuesday it will release more than 1 million tonnes of treated water from the Fukushima site in stages starting in about two years. China called the decision "extremely irresponsible", while South Korea said it will explore petitioning an international court to stop the release.

The still-struggling fishing communities of northern Japan, devastated by the earthquake and tsunami that caused the meltdowns at Fukushima 10 years ago, have long expected the decision and have lodged regular protests with the government.