Radiation leaked from a damaged Japanese nuclear reactor north of Tokyo today after an explosion blew the roof off the facility in the wake of yesterday's massive earthquake.
The developments at the Fukushima Daiichi power plant raised fears of a Chernobyl-style disaster as officials worked to contain the leak.
The Japanese plant was damaged by yesterday's 8.9-magnitude earthquake, which sent a 33ft tsunami ripping through towns and cities across the northeast coast. Kyodo news agency said more than 1,700 people were killed or missing.
Japanese authorities have told the UN's atomic watchdog they are making preparations to distribute iodine to people living near nuclear power plants affected by the earthquake, the International Atomic Energy Agency said. Iodine can be used to help protect the body from radioactive exposure.
Tokyo Electric Power Co plans to fill the leaking reactor with sea water to cool it down and reduce pressure in the unit, Japan's top government spokesman said today.
"The nuclear reactor is surrounded by a steel reactor container, which is then surrounded by a concrete building," Chief Cabinet Secretary Yukio Edano said. "The concrete building collapsed. We found out that the reactor container inside didn't explode.
"We've confirmed that the reactor container was not damaged. The explosion didn't occur inside the reactor container. As such there was no large amount of radiation leakage outside," he said.
"At this point, there has been no major change to the level of radiation leakage outside [from before and after the explosion], so we'd like everyone to respond calmly," Mr Edano said. "We've decided to fill the reactor container with sea water."
Mr Edano said it would take about five to 10 hours to fill the reactor core with sea water and around 10 days to complete the process.
He said an evacuation radius of 10km from the stricken 40-year-old Daiichi 1 reactor plant in Fukushima prefecture was adequate, but later the boundary was extended to 20km. TV footage showed vapour rising from the plant, 240km north of Tokyo.
Along Japan's northeast coast, rescue workers searched through the rubble of destroyed buildings, cars and boats, looking for survivors in hardest-hit areas such as the city of Sendai, 300km northeast of Tokyo.
The international community started to send disaster relief teams today to help Japan, with the United Nations sending a group to help co-ordinate work.
The Department of Foreign Affairs said the Irish Embassy in Tokyo had no reports as yet of any of an estimated 2,000 Irish people in Japan being injured or in need of assistance as a result of yesterday’s earthquake.
The Embassy has been contacting Irish citizens who previously registered with it in areas most affected by the quake.
It said those with family and friends in Japan may contact the department in Dublin on 01-4180233. They can also leave details on the department’s website at dfa.ie.
The earthquake yesterday was so huge that thousands fled their homes from coastlines around the Pacific Rim, as far away as North and South America, fearful of a tsunami.
Most appeared to have been spared anything more serious than some high waves, unlike Japan's northeast coastline which was hammered by the huge tsunami that turned houses and ships into floating debris as it surged into cities and villages, sweeping aside everything in its path.
The unfolding natural disaster, which has been followed by dozens of aftershocks, prompted offers of search and rescue help from 50 countries.
In one of the worst-hit residential areas, people buried under rubble could be heard calling out for rescue, Kyodo news agency reported. TV footage showed staff at one hospital waving banners with the words "Food" and "Help" from a rooftop.
In Tokyo, tens of thousands of office workers were stranded overnight after the quake shut down public transport. Many were forced to bed down where they could, with newspapers to lie on and briefcases for pillows.
Kyodo said at least 116,000 people in Tokyo had been unable to return home on Friday evening due to transport disruption.
The northeastern Japanese city of Kesennuma, with a population of 74,000, was hit by widespread fires and one-third of the city was under water. The airport in coastal city Sendai, home to one million people, was on fire, Japanese media said.
TV footage showed a black torrent of water carrying cars and wrecked homes at high speed across farmland near Sendai, 300km northeast of Tokyo. Ships had been flung onto a harbour wharf.
Italy's National Institute of Geophysics and Volcanology said the Earth's axis shifted 25 cm as a result of the quake and the US Geological Survey said the main island of Japan had shifted 2.4 metres.
The earthquake was the fifth most powerful to hit the world in the past century. It surpassed the Great Kanto quake of September 1st, 1923, which had a magnitude of 7.9 and killed more than 140,000 people in the Tokyo area.
The 1995 Kobe quake caused $100 billion in damage and was the most expensive natural disaster in history.
Reuters