The head of the UN atomic agency observed first-hand the Fukushima Daiichi nuclear power plant's ongoing radioactive wastewater discharges for the first time since the contentious programme began months ago and called it an "encouraging start.”

International Atomic Energy Agency (IAEA) Director-General Rafael Grossi watched treated radioactive water being mixed with massive amounts of seawater and examined a water sampling station. He was escorted by utility Tokyo Electric Power Company Holdings president Tomoaki Kobayakawa.

The discharges have been opposed by fishing groups and neighbouring countries, some of which banned all imports of Japanese seafood immediately after the release began.

A 2011 earthquake and tsunami damaged the Fukushima plant’s power supply and reactor cooling functions, triggering meltdowns of three reactors and causing large amounts of radioactive wastewater to accumulate.

After more than a decade of cleanup work, the plant began discharging the water after treating it and diluting it with seawater on August 24, starting a process that’s expected to take decades.

Grossi last visited the plant in July after issuing an IAEA review predicting only negligible impact from the discharges. An IAEA comprehensive report later concluded that the discharges meet international safety standards.

Grossi said an IAEA office and a laboratory at the plant have been carrying out their own, independent evaluations of the discharges, and results had been in line with what they expected.

“We never say ‘this is done’ or ‘this is okay’ because there is a long way to go," he said. “I would say it's a very positive and encouraging start.”

Grossi also met with local officials and representatives from fishing and business groups and reassured them that the discharges are being carried out “with no impact to the environment, water, fish and sediment.” (AP)