Prime Minister Fumio Kishida on Monday urged China to rein in a barrage of harassing phone calls and slammed incidents of rock-throwing at Japanese schools and its embassy in Beijing, following Tokyo’s decision last week to release treated water from the Fukushima No. 1 nuclear power plant into the Pacific Ocean.

"There have been numerous harassing phone calls thought to have originated in China, and instances of stones being thrown at the Japanese Embassy and Japanese schools" in China, Kishida told reporters. "I must say that these are regrettable."

Kishida noted Japan's decision earlier Monday to summon China's ambassador, with the Japanese government "strongly urging him to call on Chinese people to act in a calmly and responsibly."