The Chinese embassy in Japan said on Thursday that repeated accidents in the process of treating Fukushima nuclear-contaminated water have exposed the disorderly management of Tokyo Electric Power Company (TEPCO) and the Japanese government.

"It has once again proved that the equipment used for treatment of nuclear-contaminated water is not reliable in the long run and further highlights the need for the international community to carry out supervision," the embassy said in a statement.

The statement came after tonnes of radioactive water got leaked on Wednesday from a device treating nuclear-contaminated water at the tsunami-stricken Fukushima Daiichi Nuclear Power Plant.

TEPCO said the environment outside the plant was unaffected but estimated that up to 5.5 tonnes of radioactive water, containing 22 billion becquerels of radioactive substances, got leaked after valves on water treatment equipment were left open during maintenance work.