In a move that has caused alarm among neighbouring countries and local fishermen, Japan is set to start releasing over one million tonnes of water from the wrecked Fukushima Dai-ichi Nuclear Power Plant this summer. China has emerged as the most vocal of those critics, saying the plan would endanger the environment and human lives.

At a meeting with Wang on the sidelines of an Association of Southeast Asian Nations (ASEAN) meeting in Indonesia, Hayashi said Japan was willing to communicate with China about the water discharge from a scientific perspective, according to the Japanese foreign ministry.

"(Hayashi) called on China to respond in a scientific manner," it said in a statement.

The issue of the water release took up a substantive amount of the hour-long talk between Wang and Hayashi, but the two did not come to a clear agreement on the matter, a Japanese foreign ministry official told reporters later on Friday.

Although China has raised concerns about the water discharge, a comprehensive review of the plan by the United Nations nuclear watchdog has said that the impact will be "negligible" and that the discharge will be in accordance with international standards.

The Japanese government says the water has been filtered to remove most radioactive elements except for tritium, an isotope of hydrogen that is hard to separate from water. The treated water will be diluted to well below internationally approved levels of tritium before being released into the Pacific.

Hayashi defended the plan at an ASEAN meeting on Thursday and asserted that China was making "claims not rooted in scientific evidence", according to Japan's foreign ministry.

Relations between the two countries have also become tense as China asserts its maritime ambitions in the region, which Hayashi touched on during his meeting with Wang.

Hayashi "conveyed strong concerns over China's increasing military activity conducted within the vicinity of Japan" as well as Chinese military cooperation with Russia, according to the statement.

(Reporting by Sakura Murakami; editing by Himani Sarkar, Michael Perry and Mark Heinrich)

By Sakura Murakami