Highly radioactive water from Japan's crippled Fukushima nuclear plant is pouring out at a rate of 300 tonnes a day, officials said on Wednesday (August 7), as Prime Minister Shinzo Abe ordered the government to step in and help in the clean-up.

The admission indicates that two and a half years after the plant was hit by a huge earthquake and tsunami, plant operator Tokyo Electric Power Co (Tepco), which only recently admitted water had leaked at all, has yet to come to grips with the worst nuclear disaster since Chernobyl.

Tepco officials said the company was moving with haste, but refused to confirm the extent of the leak.

A research team led by the Institute of Industrial Sciences of the University of Tokyo has been mapping radioactivity on the bottom of the sea around the nuclear plant.

On Wednesday, they said they had found off shore of Fukushima multiple hotspots that were several times higher in radioactive cesium-137 readings than the surrounding seabed.

The newly acknowledged leak from the plant 220 km (130 miles) northeast of Tokyo is enough to fill an Olympic swimming pool in barely a week. The water is spilling into the Pacific Ocean, but it was not immediately clear how much of a threat it poses.

In the early weeks of the disaster, the Japanese government allowed Tepco to dump tens of thousands of tonnes of contaminated water into the Pacific in an emergency move.

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