Japan has complained to the Chinese government after businesses and institutions began receiving volumes of abusive phone calls about the release of contaminated water from the damaged Fukushima plant.
The calls come from numbers with Chinese dialling codes.
One restaurant chain in Fukushima has received more than 1,000 calls.
It comes as Tokyo said seawater around the nuclear plant is showing no detectable levels of radioactivity.
The calls had begun since the release of contaminated water from Fukushima, authorities said, and have been made to government departments, schools and even an aquarium.
The callers speak in Chinese, Japanese and English – and sometimes use abusive language. They speak about their opposition to Japan’s decision to release the treated nuclear water.
China has described the discharge as an “extremely selfish and irresponsible act”.
On Thursday it said it would ban Japanese seafood imports.
Meanwhile, Tokyo is hoping regular radiation testing in the waters near the plant will allay concerns from neighbouring countries and fishing groups.
Weekly test results will be published for the next three months.
More than a million tonnes of water stored at the nuclear plant will be discharged over the next 30 years.
