VIENNA -- A Chinese nuclear official on Monday lambasted Japan's "irresponsible" release of nuclear-contaminated wastewater from the crippled Fukushima Daiichi Nuclear Power Plant into the sea at the General Conference of the International Atomic Energy Agency (IAEA).

China actively supports the IAEA's efforts to safeguard international peace and security, and to promote the peaceful use of nuclear energy and nuclear technologies for better benefiting developing countries, said Liu Jing, vice chairman of the China Atomic Energy Authority, during the general debate of the conference held here.

Ignoring the doubts of the international community and the strong opposition from the people of relevant countries, Japan has obstinately started the Fukushima wastewater discharge plan, which has raised international concerns, he said.

The discharge of the Fukushima wastewater is a major nuclear safety issue, as it is an unprecedented artificial release of contaminated water from nuclear accidents into the sea, and there is a lot of uncertainty about the cumulative effect caused by the release of large quantities of radionuclides into the sea, Liu said, noting that Japan has failed to give a credible and scientific response to the international outcry.

He urged the IAEA to establish a long-term and effective international monitoring mechanism to strictly supervise Japan's irresponsible moves and prevent the Fukushima wastewater discharge from causing long-term harm to the marine environment and human health.

The Chinse official also met with IAEA Director General Rafael Grossi on Monday on the sidelines of the IAEA general conference, and elaborated on China's position on Japan's release of the Fukushima nuclear-contaminated wastewater.

Grossi said that he attaches great importance to China's relevant position and concerns, and is willing to maintain close communication and cooperation with China in this regard.

The 67th IAEA General Conference opened here Monday and will run until Friday.