Wu said Japan's relevant decision disregarded the global marine environment, the safety of international public health, and the security interests of people from the surrounding countries.
He said such a decision is a violation of international law and rules and should not be a behavior of a modern civilized country.
"China is strongly dissatisfied with and firmly opposes this decision," Wu said.
China urges Japan to recognize the responsibilities it shoulders and fulfill its international obligations in a scientific manner, said Wu.
He said that Japan should review the issue of disposing of the wastewater from the Fukushima nuclear plant and withdraw its decision to dump the wastewater into the sea.
Wu said a joint technical working group, which includes Chinese experts, should be set up under the framework of the international institutions, to ensure that the disposal of nuclear wastewater is strictly under international evaluation, checks, and supervision.
Before reaching a consensus with all relevant stakeholders and international institutions through consultations, Japan should not discharge the nuclear wastewater into the sea, said Wu.
He added that China will, together with the international community, continue to closely watch the development of the matter and reserves the right to make further responses.