Radiation alert in Japan following third blast at nuclear plant

The government has confirmed that radiation from the Fukushima Daiichi nuclear plant has reached harmful levels

Japan could be on the brink of one of the world's biggest nuclear catastrophes, after a third explosion and a fire at the Fukushima Daiichi plant this morning has resulted in radiation reaching hamful safe levels.

Reactor 2 became the third vessel to explode within four days at the plant, which sits 155 miles north-east of Tokyo.

Officials fear this latest explosion may have caused a crack in the reactor, which would be the first time a vessel has been breached since the troubles started, allowing steam contining radioactive substances to seep into the atmosphere.

A high radioactivity reading has been recorded near the site, which may have been caused by a breach to reactor 2, or the fire that started at reactor 4.

Technicians continue to attempt to cool the reactors by getting enough water to them, but many personnel have been ordered to leave the plant and its vicinity, and those there are only allowed to work for brief periods.

Prime Minister Naoto Kan advised citizens via a TV address: 'Radiation has spread from these reactors and the reading of the level seems high ... There's still a very high risk of further radioactive material coming out.'

He stated that all residents within the 12-mile exclusion zone should leave immediately, and that those within 12-19 miles should stay in their homes and ensure they close all windows and keep their houses airtight.

A no-fly zone was also imposed for a 19-mile radius around the plant, to prevent planes spreading radiation.

In Tokyo, radiation levels were recorded to be slightly higher than normal, but far below those that may pose health risks.

Following Friday's devastating earthquake and tsunami, 2,400 people have been confirmed dead, although thousands remain missing.

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