China on Thursday banned all Japanese seafood imports over what it said was the "selfish" release of wastewater from the crippled Fukushima nuclear plant.

Japan began discharging treated contaminated water from the stricken plant into the Pacific Ocean on Thursday in an operation it insists is safe but which has generated a fierce backlash from China.

Beijing's foreign ministry branded the release as an "extremely selfish and irresponsible act", saying in a statement that the move would "push the risks onto the whole world (and) pass on the pain to future generations of human beings".

And China's customs authority said it would "suspend the import of aquatic products originating in Japan from August 24, 2023, including edible aquatic animals".

The decision was taken to "comprehensively prevent the food safety risks of radioactive contamination caused by the discharge of nuclear wastewater from Fukushima into the sea", the General Administration of Customs said.

It would also "protect the health of Chinese consumers and ensure the safety of imported food", the authority added.

Beijing had already suspended all food imports from 10 out of 47 Japanese prefectures in July, with Hong Kong following suit.

China imported over $500 million worth of seafood from Japan last year, according to customs data.

In 2011, three reactors at the Fukushima-Daiichi facility in northeastern Japan went into meltdown following a massive earthquake and tsunami that killed around 18,000 people.

Since then, plant operator TEPCO has collected 1.34 million cubic metres of water contaminated as it cooled the wrecked reactors, along with groundwater and rain that has seeped in.

The beginning of the discharge of around 540 Olympic swimming pools' worth of water over several decades is a big step in decommissioning the still highly dangerous site.

The release of the wastewater has been deemed safe by the International Atomic Energy Agency.

But China's foreign ministry said Thursday that "the ocean is the common property of all humanity, and forcibly starting the discharge of Fukushima's nuclear wastewater into the ocean... ignores international public interests".

Japan "did not prove the legitimacy" of the plan or the "long-term reliability of the nuclear wastewater purification equipment", it said.

Tokyo also "did not prove the authenticity and accuracy of the nuclear wastewater data, (and) did not prove that ocean discharge is harmless to the marine environment and human health".

"By treating the release of the wastewater as a fait accompli, the Japanese side has simultaneously placed itself in the international dock," the ministry added.

"The Japanese side should not cause secondary harm for local people or even the people of the world out of its own self-interest."

Sign up to our free newsletters

Get the best updates straight to your inbox:
Please select at least one mailing list.

You can unsubscribe at any time by clicking the link in the footer of our emails. We use Mailchimp as our marketing platform. By subscribing, you acknowledge that your information will be transferred to Mailchimp for processing.