Despite opposition from its neighbors, Japan will begin releasing treated radioactive water from the tsunami-hit Fukushima nuclear plant on Thursday.

The UN’s nuclear watchdog approved the plan weeks ago.

Since the 2011 tsunami destroyed the plant, 1.34 million tonnes of water have accumulated – enough to fill 500 Olympic-sized pools.

After filtration and diluting, the water will be released over 30 years.

Japan’s Prime Minister Fumio Kishida said after a Cabinet meeting on Tuesday that authorities will request the plant’s operator to “promptly prepare” for the disposal to begin on 24 August if weather and sea conditions permit.

As a result of Mr Kishida’s visit to the plant on Sunday, speculation was rife that the release was imminent.

Decommissioning the plant, located on the east coast about 220km (137 miles) north-east of Tokyo, is a lengthy and costly process, and releasing the water is a necessary step.

For more than a decade, Japan has been collecting and storing contaminated water in tanks, but space is running out. Since it was approved by the Japanese government two years ago, the plan to release water from the plant has caused alarm across Asia and the Pacific.

It had been signed off by the UN’s nuclear watchdog, which concluded that the impact on people and the environment would be negligible, but fishermen still fear that discharging the treated water will tarnish the reputation of their catch and adversely affect their livelihoods.

Tepco has filtered the water to remove more than 60 radioactive substances, but the water will still contain tritium and carbon-14, radioactive hydrogen and carbon isotopes that cannot be easily removed from water. Although they emit very low levels of radiation, experts believe they are not a danger unless consumed in large quantities.

China has been the most vocal opponent of the plan in neighbouring countries. Japan was accused of treating the ocean like a “private sewer.”

However, South Korea has endorsed the plan and accused protesters of scaremongering.

Fukushima residents are also skeptical that the treated water will be safe, and many fishermen are worried that the release will affect their livelihoods.

Fish imports from Fukushima have been banned in both South Korea and China.