The Japanese embassy in Beijing is on high alert for possible strong reactions after Japan started to release treated and diluted water into the ocean from the crippled Fukushima Daiichi nuclear power plant on Thursday.

China strongly opposes the action despite the water being treated and diluted to reduce its tritium levels to about one-seventh of the World Health Organization's guidelines for drinking water. The country immediately suspended all imports of seafood from Japan.

Embassy officials say abusive phone calls are being made from China to individuals and organizations in Japan that are unrelated to the release.

The embassy has called on Chinese authorities to take strict action in accordance with law.

A concert featuring a Japanese pianist, scheduled to be held at the embassy on Saturday, was postponed. Organizers cited security concerns as the event would be attended by Japanese residents.

When the Japanese government purchased the Senkaku Islands in Okinawa Prefecture from a private Japanese owner in 2012, some anti-Japanese demonstrations grew violent, and inflicted damage to Japanese companies and department stores.

Japan controls the islands. The Japanese government maintains the islands are an inherent part of Japan's territory. China and Taiwan claim them.

So far this time, no major troubles have been confirmed. However, the embassy says the possibility of unexpected developments cannot be ruled out. It is warning Japanese residents to act cautiously and refrain from speaking Japanese loudly when they go out.