Japanese stocks fell sharply in Tuesday morning trading as investor sentiment was hurt by reports that the government would raise the accident level at a damaged nuclear power plant to 7, the worst on an international scale.

The Nikkei 225 Stock Average lost 155.77 points, or 1.6 per cent, to trade at 9,563.93 while the broader Topix index was down 11.82 points, or 1.39 per cent, at 840.52.

The government raised the level at the Fukushima Daiichi Nuclear Power Station from 5 to 7 late in the morning. Level 7 had only been applied previously to the 1986 Chernobyl disaster.

The accident level was elevated after the government’s Nuclear and Industrial Safety Agency determined that the plant has been releasing massive amounts of radioactive materials, which are posing threats to human health and the environment over a wide area, the public broadcaster NHK reported.

The plant was severely damaged by the March 11 earthquake and tsunami. Its power was knocked out and its cooling functions failed, leading to overheating, explosions and radiation leaks.

For a month, the government and the plant’s operator, the Tokyo Electric Power Co, have been struggling to stabilize the plant.

On currency markets at 11:08 am (0208 GMT), the dollar traded at 84.22—24 yen, down from Monday’s 5 pm quote of 84.74-76 yen.

The euro traded at 1.4408-4410 dollars, down from 1.4459-4461 dollars Monday, and at 121.36-40 yen, down from 122.53-57 yen.

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