Japanese phones shrilling in protest

Tokyo has urged Beijing to "ensure the safety of Japanese residents in China" after a wave of telephone harassment targeting businesses in Japan sparked by the discharge of Fukushima wastewater.

While Japan insists the release of the treated water is safe - a claim backed by the UN's nuclear watchdog - China has staunchly opposed it and banned all Japanese seafood imports, saying it contaminates the ocean.

Calls from China began flooding Japanese businesses from Thursday, when operator Tepco started releasing water used to cool the stricken nuclear reactors at the Fukushima Daiichi plant on the east coast.

Japanese businesses and groups, ranging from a concert hall in Tokyo to an aquarium in Iwate, reported receiving so many calls from Chinese speakers they had difficulty conducting operations.

Hiroyuki Namazu, in charge of Asian and Oceanian affairs for Japan, told officials at the Chinese embassy in Tokyo to call for calm in their country.

Similar incidents have also occurred in China against Japanese facilities, Namazu told embassy officials.

"We strongly urge the Chinese government to take appropriate measures, such as calling on its citizens to act calmly, and to take all possible measures to ensure the safety of Japanese residents in China and Japanese diplomatic missions in China."

Tokyo's embassy in Beijing has also urged its nationals there to refrain from speaking loudly in Japanese.

A Fukushima businessperson told Kyodo news agency that his four restaurants and pastry shops received about 1,000 calls on Friday, mostly from China, so his businesses had to unplug their phones.

Fukushima city mayor Hiroshi Kohata said on Saturday that his city hall had received around 200 similar calls in two days, while local schools, restaurants and hotels were also targets.

"I will report this to the Japanese government and demand action," he said.

In China, people posted videos of themselves making calls to Japanese numbers, including restaurants in Fukushima.