Fukushima nuclear disaster now on par with Chernobyl in wake of more quakes

Japan is to raise its assessment of the severity of its nuclear emergency to the maximum seven on an international scale, putting it on a par with Chernobyl.

At the same time, increasing radiation has prompted the government to widen the evacuation zone and as earthquake aftershocks rocked the country.

How it all began ... TEPCO has released pictures of flooding at its Fukushima Dai-ichi nuclear power plant when the March 11 tsunami hit.Credit: AP

The news comes as engineers fighting a fire at Japan's crippled Fukushima nuclear power station following the aftershock, which swayed buildings in central Tokyo and closed Narita airport runways.

Japan's Nuclear and Industrial Safety Agency raised the rating to 7, and will announce the decision at a news conference today, national broadcaster NHK reported. The accident at Tokyo Electric Power's station is currently rated 5 on the global scale, the same as the 1979 partial reactor meltdown at Three Mile Island in Pennsylvania in the '70s.

The stricken nuclear plant, about 220 kilometres north of Tokyo, is leaking radiation in Japan's worst civilian nuclear disaster following a magnitude 9 quake and tsunami on March 11.

The power station has withstood hundreds of aftershocks, and the government widened the surrounding evacuation zone yesterday.

A magnitude-6.4 earthquake struck off the coast of Chiba, the prefecture east of Tokyo, this morning, swaying buildings in the capital, according to the US Geological Survey. This followed a 6.6-magnitude temblor yesterday and a magnitude 7.1 aftershock on April 7.

The fire at the sampling building near the No. 4 reactor at the Fukushima Dai-Ichi station was extinguished this morning. The fire was not related to this morning's quake, a spokesman for the company said.

The aftershock also affected bullet train services in the Tokyo area, with services suspended to allow the system to be checked. Services have since been resumed.

Agencies