Japan earthquake: panic in Tokyo as radiation spreads.
Panic has begun to spread Tokyo after elevated levels of radiation were detected in one of the world's largest metropolises.
Last night Fukushima nuclear plant was hit by a third explosion, this time at the No.2 reactor.
The International Atomic Energy Agency also announced that a spent fuel storage pond at the plant's No. 4 reactor was on fire, and radioactivity was being released directly into the atmosphere.
People living up to six miles beyond an existing 12 mile exclusion zone around the nuclear plant have been advised to stay indoors.
In comments that marked a dramatic escalation in the official assessment of the dangers Prime Minister Naoto Kan said radiation around the Fukushima 1 plant had "risen considerably."
He said: "There has been a fire at the No. 4 reactor and radiation levels in the surrounding area have heightened significantly.
"The possibility of further radioactive leakage is heightening.
"We are making every effort to prevent the leak from spreading. I know that people are very worried but I would like to ask you to act calmly."
Twelve million people live in the Japanese capital and there were fears that the effects of the explosions and fire at three nuclear reactors could spread there.
The French embassy said a low-level "radioactive wind" could reach the capital by 8pm (11am GMT) and warned its citizens to leave.
In a sign of mounting fears about the escalating nuclear disaster Air China, China's national airline, cancelled its flights to Tokyo.
Sairi Koga, an official of the Tokyo Metropolitan Government, said: "We monitored a higher than normal amount of radiation in the morning in Tokyo.
"But we don't consider it to be at a level where the human body is affected."
The Kyodo news agency reported that that the levels in the capital were "minute."
But it also reported that radiation levels in Saitama, just outside Tokyo, were 40 times usual levels, although still not harmful to health.
Winds from the stricken Fukushima Daiichi nuclear plant were travelling in a south-westerly direction towards Tokyo, 155 miles away, at two to three metres per second.
Some residents left the capital and others stocked up on food and supplies in case they were required to stay indoors. Shops sold out of items like radios, torches and candles.
Some multinational companies either urged staff to leave or said they were considering plans to move outside Tokyo.
The Czech Symphony Orchestra left the Japanese capital by bus for the west coast after their concert in Tokyo was cancelled.
The German embassy urged all its citizens to register on a "crisis list" and to consider leaving Japan.
The Japanese government warned radiation levels near the stricken plant are now harmful to human health.
It has already imposed an exclusion zone 20km, and asked people up to 30km away to stay indoors as it battles a potential meltdown.
Following explosions at three of the reactors a fire broke out at a fourth. The fire was later extinguished.
Chief Cabinet Secretay Yukio Edano said: "It is likely that the level of radiation increased sharply due to a fire at Unit 4.
"Now we are talking about levels that can damage human health.
"The radiation spread will depend on the wind speed and direction The further away you move the lower the radiation levels will become.
"Beyond 30km the harm to human health would be minimal or none at all."
Leaks of radioactive material at the plant followed last Friday’s devastating earthquake and tsunami in which more than 10,000 people are thought to have died.
It is the worst nuclear accident since the Chernobyl disaster in Ukraine in 1986.
Kaoru Hashimoto, 36, a housewife living in Fukushima city said: "What we most fear is a radiation leak from the nuclear plant. Not much confirmed information is coming to us, so we are in trouble about how to cope with the situation."
At one nearby shelter, a young woman holding her baby told public broadcaster NHK: "I didn't want this baby to be exposed to radiation. I wanted to avoid that, no matter what."
Japanese stocks plunged more than 14 per cent —eading for their biggest drop since 1987.