The Tokyo Metropolitan Government is using a recorded message to deal with harassing phone calls, apparently coming from China, protesting the release of treated and diluted water from the Fukushima Daiichi nuclear power plant.
Public facilities and businesses across Japan have been receiving such international phone calls from numbers starting with China's country code 86 since the water release began on August 24.
The Metropolitan Government says that by the end of last month it had received more than 34,000 calls.
Starting last Friday, Tokyo officials are using a system to automatically play a recorded message when suspicious calls come from China.
The message says in Chinese that the release of the treated water into the sea is in line with international standards and customs.
It says the water is diluted to reduce tritium levels to below those of nearby countries, and that thorough measures are taken to ensure the safety of the water.
Tokyo officials say that after its introduction, the new message system responded to 198 calls during the first 105 minutes.
An official says they decided to take the step because it is necessary to give correct information as some calls were based on misunderstanding.
The Fukushima Daiichi plant suffered a triple meltdown in the 2011 earthquake and tsunami. Water used to cool molten fuel at the plant has been mixing with rain and groundwater.
The accumulated water is treated to remove most radioactive substances, but still contains tritium.
Before releasing the treated water into the sea, the plant's operator dilutes it to reduce tritium levels to about one-seventh of the World Health Organization's guidelines for drinking water.