Explosions and a fire at Japan's quake-hit nuclear plant unleashed dangerous levels of radiation on Tuesday, sparking a collapse on the stock market and panic-buying in supermarkets.
Two women cover their mouths against the threat of radiation at Yamada town in Iwate Prefecture.
Tokyo stocks, which were punished Monday in a frantic sell-off that sent indexes around the world sliding, plummeted another 14 percent Tuesday before paring some losses and ending 10.55 percent down.
In towns and cities, fearful citizens stripped shelves of food and water, prompting the government to warn that panic-buying could hurt its ability to provide aid to areas devastated by Friday's massive quake and tsunami.
But scared Tokyo residents filled outbound trains and rushed to shops to stock up on face masks and emergency supplies amid heightening fears of radiation headed their way.
Radiation levels around the Fukushima No.1 plant on the eastern coast had "risen considerably", Prime Minister Naoto Kan said, and his chief spokesman announced it had reached the point where it endangered human health.
In Tokyo, 250 kilometres (155 miles) to the southwest, authorities also said that higher-than-normal radiation levels had been detected in the capital, the world's biggest urban area, but not at harmful levels.
Kan warned people living up to 10 kilometres (six miles) beyond a 20 km exclusion zone around the nuclear plant to stay indoors.
"I would like to ask the nation, although this incident is of great concern, I ask you to react very calmly," he said.
The fire, which was later extinguished with the help of US troops, broke out in the plant's number-four reactor, meaning that four out of six reactors at the facility were in trouble -- and temperatures were reportedly rising in the other two.
Radiation levels later dropped at both the plant and in Tokyo, chief government spokesman Yukio Edano said.
The UN weather agency said that winds were currently blowing radioactive material towards the ocean, and that there were "no implications" for Japan or countries nearby.
France's Nuclear Safety Authority said the disaster now ranked at six on a seven-point international scale of gravity for nuclear accidents, ranking the crisis second only in gravity to Chernobyl.
The disaster also prompted Russia and Germany to order immediate reviews of their atomic energy sectors, with Berlin saying it would provisionally shut down seven nuclear reactors for three months pending a safety assessment.
On top of the atomic emergency, Japan is struggling to cope with the enormity of the damage from the record quake and the tsunami that raced across vast tracts of its northeast, destroying all before it.
The official death toll rose to 2,414, police said Tuesday, but officials have said at least 10,000 were likely to have perished.
In the only country in the world to have experienced a nuclear attack -- two bombs dropped by the United States during World War II killed some 200,000 people -- Japanese citizens are gripped by fear of nuclear fallout.
"What we most fear is a radiation leak from the nuclear plant," Kaoru Hashimoto, 36, a housewife living in Fukushima city, 80 kilometres (50 miles) northwest of the stricken plant, told AFP by phone.
Hashimoto said supermarkets were open but shelves were completely empty. "Many children are sick in this cold weather but pharmacies are closed. Emergency relief goods have not reached evacuation centres in the city.
"Everyone is anxious and wants to get out of town. But there is no more petrol."
More than 200,000 people have already been evacuated from the exclusion zone around the crippled plant.
At one 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."
The crisis at the ageing Fukushima nuclear plant has worsened daily since Friday's quake and tsunami knocked out cooling systems.
Explosions hit the buildings housing reactors one and three Saturday and Monday. On Tuesday, a blast hit reactor two at the plant and there was also an explosion at reactor four which started a fire.
Government spokesman Edano said radioactive particulates leaked along with the hydrogen.
The UN's nuclear watchdog, the International Atomic Energy Agency, said Tokyo had asked for expert assistance in the aftermath of the quake, which US seismologists are now measuring at 9.0-magnitude, revised up from 8.9.
But the IAEA's Japanese chief Yukiya Amano moved to calm global fears that the situation could escalate to rival the world's worst nuclear accident at Chernobyl in Ukraine in 1986.
"Let me say that the possibility that the development of this accident into one like Chernobyl is very unlikely," he said.
The devastation in tsunami-hit areas such as Sendai city in the northeast, however, is absolute.
At the once-bustling regional airport small planes jutted out at awkward angles from thick mud, amid the wreckage of clusters of wooden beachfront houses that were splintered into flotsam in an instant by the waves.
As far as the eye can see, the machinery of modern life has been crumpled almost beyond recognition -- cars are stuck incongruously into the few remaining structures or balanced on top of wrecked homes.
Aid workers and search teams from across the world have joined 100,000 Japanese soldiers in a massive relief push in the shattered areas.
Rescuers on Tuesday pulled two survivors, an elderly woman and a man, from underneath the rubble, four days after the earthquake, public broadcaster NHK reported.
Millions have been left without water, electricity, fuel or enough food and hundreds of thousands more are homeless and facing harsh conditions with sub-zero temperatures overnight, and snow and rain forecast.
The government expects a "considerable" economic impact from the disaster, which has plunged the nation into what Prime Minister Kan called its worst crisis since World War II.
Singapore's DBS Bank estimated that the twin disasters would cost Japan's economy about $100 billion, or about two percentage points of its annual gross domestic product.