Panic swept Tokyo on Tuesday as radiation levels surged there, causing some to leave the capital and others to stock up on food and supplies before levels dropped again by evening.
The spike came after a third explosion in four days rocked the tsunami-damaged Fukushima Dai-ichi plant earlier Tuesday.
Several embassies advised staff and citizens to leave affected areas, tourists cut short vacations and multinational companies either urged staff to leave or said they were considering plans to move outside Tokyo.
Japan told the International Atomic Energy Agency that a spent fuel storage pond caught fire at a reactor and radioactivity had been "released directly into the atmosphere." The blaze was later extinguished and the U.N. nuclear watchdog later said radioactivity levels near the nuclear site fell during a six-hour period on Tuesday.
Officials in Tokyo — 150 miles to the south of the plant — said radiation in the capital was 10 times normal by evening but there was no threat to human health. Around eight hours after the explosion, the U.N. weather agency said winds were dispersing radioactive material over the Pacific Ocean, away from Japan and other Asian countries.
Radiation levels in Saitama, near Tokyo, were 40 times normal levels — not enough to cause human damage but enough to stoke panic in the bustling metropolis of about 12 million people.
Still, the French Embassy in Tokyo advised its citizens to leave the Japanese capital. The U.S. government advised Americans to avoid travel to Japan.
Austria moved its embassy from Tokyo to Osaka.
China became the first government to organize a mass evacuation of its citizens from Japan's northeast. Air China and China Eastern Airlines also canceled flights to Tokyo and two cities in the disaster area.
German airline Lufthansa started scanning aircraft returning from Japan for radioactivity, NBC News reported. "This is a precautionary measure for us," a spokesman said.
Radiation levels also rose slightly in Russia's Far East on Tuesday but stayed within normal levels, local officials said.
Russia's military said it was on alert to evacuate people if required from Russia's Sakhalin island, whose southernmost tip is visible from northern Japan, Interfax news agency reported.
Shopping frenzyIn Tokyo, canned goods, batteries, bread and bottled water vanished from store shelves and long lines of cars circled gas stations as the nuclear crisis set off panic-buying.
Far outside the disaster zone, stores were running out of necessities, raising government fears that hoarding may hurt the delivery of emergency food aid to those who really need it.
The frenzied buying has compounded supply problems from damaged and congested roads, stalled factories, reduced train service and other disruptions caused by Friday's earthquake and tsunami.
Tourists such as Christy Niver, of Egan, Minn., said they had had enough and were leaving. Her 10-year-old daughter, Lucy, was more emphatic. "I'm scared. I'm so scared I would rather be in the eye of a tornado," she said. "I want to leave."
Even in the western city of Hiroshima, which was untouched by the disaster, stores are running out of batteries and the media was warning people not to hoard, a local government official said.
U.S. banking giant Citigroup said it was keeping workers in Tokyo informed but there were no evacuation orders, said a spokesman, adding the bank was closely following guidance by the U.S. Embassy.
Some international journalists covering the disaster from the worst-hit region around the northeastern city of Sendai were pulling out.
One scientist, however, urged people in Tokyo to stay calm.
"Radioactive material will reach Tokyo but it is not harmful to human bodies because it will be dissipated by the time it gets to Tokyo," said Koji Yamazaki, professor at Hokkaido University graduate school of environmental science.
"If the wind gets stronger, it means the material flies faster but it will be even more dispersed in the air."
Hundreds of aftershocks have shaken Japan's northeast and Tokyo since the original offshore quake, including one Tuesday night whose epicenter was hundreds of miles (kilometers) southwest and inland.
Some wanted the government to expand the 18 mile evacuation zone surrounding the nuclear plant. "The evacuation zone may not be enough," said a scientist who treats nuclear radiation victims.
"The main lasting effect will probably be in milk produce and the radiation in milk because the cows go around like vacuum cleaners and absorb the radiation spread over a wide range," said the expert, who declined to be identified. "Those particles are easily transferred into the milk, which is in turn easily absorbed by babies and children."
In a rare bit of good news, rescuers found two survivors Tuesday in the rubble left by the tsunami that hit the northeast, including a 70-year-old woman whose house was tossed off its foundation.