"There have been numerous harassment calls believed to originate from China and instances of stones being thrown into the Japanese embassy and Japanese schools. It must be said these are regrettable," Fumio Kishida told reporters.

"We summoned the Chinese ambassador to Japan today and strongly urged him to call on Chinese people to act in a calm and responsible manner," Kishida added.

"Even after the ocean release, the United States, for example, expressed its position that it is satisfied with Japan's safe, highly transparent and scientifically justified process. We would like to convey these voices from the international community to the Chinese government."

Japan has begun releasing more than 500 Olympic swimming pools' worth of treated wastewater from Fukushima into the Pacific, 12 years after a tsunami knocked out three reactors in one of the world's worst atomic accidents.

China in response banned all seafood imports from its neighbour.