By Shinichi Saoshiro and Chisa Fujioka
TOKYO (Reuters) - Workers were ordered to withdraw from a stricken Japanese nuclear power plant on Wednesday after radiation levels rose, Kyodo news reported, a development that suggested the crisis was spiraling out of control.
Just hours earlier another fire broke out at the plant, which has sent low levels of radiation wafting into Tokyo in the past 24 hours, triggering international alarm.
Japan's chief government spokesman said it was "not realistic" to think the Daiichi nuclear plant in Fukushima, 240 kms (150 miles) north of Tokyo, would reach the start of a nuclear chain reaction, but said officials were talking to the U.S. military about possible help.
While public broadcaster NHK said flames were no longer visible at the building housing the No.4 reactor of the plant, TV pictures showed smoke or steam rising from the facility around 0100 GMT.
Academics and nuclear experts agree that the solutions being proposed to contain damage to the reactors are last-ditch efforts to stem what could well be remembered as one of the world's worst industrial disasters.
"This is a slow-moving nightmare," said Dr Thomas Neff, a research affiliate at the Center for International Studies, which is part of the Massachusetts Institute of Technology.
Concern had earlier been mounting that the skeleton crews dealing with the crisis might not be big enough, or were possibly exhausted after working for days since Friday's massive earthquake damaged the facility. Authorities had withdrawn 750 workers on Tuesday, leaving only 50.
The plight of hundreds of thousands left homeless by the quake and devastating tsunami that followed worsened overnight following a cold snap that brought snow to some of the worst-affected areas.
While the official death toll stands at around 4,000, more than 7,000 are listed as missing and the figure is expected to rise.
In the first hint of international frustration at the pace of updates from Japan, Yukiya Amano, director general of the International Atomic Energy Agency, said he wanted more timely and detailed information.
"We do not have all the details of the information so what we can do is limited," Amano told a news conference in Vienna. "I am trying to further improve the communication."
Several experts said that Japanese authorities were underplaying the severity of the incident, particularly on a scale called INES used to rank nuclear incidents. The Japanese have so far rated the accident a four on a one-to-seven scale, but that rating was issued on Saturday and since then the situation has worsened dramatically.
France's nuclear safety authority ASN said Tuesday it should be classed as a level-six incident.
Japanese Prime Minister Naoto Kan on Tuesday urged people within 30 km (18 miles) of the facility -- a population of 140,000 -- to remain indoors, as authorities grappled with the world's most serious nuclear accident since the Chernobyl disaster in Ukraine in 1986.
Officials in Tokyo said radiation in the capital was 10 times normal at one point but not a threat to human health in the sprawling high-tech city of 13 million people.
But residents have nevertheless reacted to the crisis by staying indoors. Public transport and the streets are as deserted as for a public holiday and scores of shops and offices closed.
Winds over the plant will blow from the north along the Pacific coast early on Wednesday and then from the northwest toward the ocean during the day, the Japan Meteorological Agency said.
Fears of transpacific nuclear fallout sent consumers scrambling for radiation antidotes in the U.S. Pacific Northwest and Canada. Authorities warned that people would expose themselves to other medical problems by needlessly taking potassium iodide in the hope of protection from cancer.
The nuclear crisis and concerns about the economic impact from last week's earthquake and tsunami have hammered Japan's stock market.
The Nikkei index ended the morning up 4.37 pct after closing down 10.6 percent on Tuesday and 6.2 percent the day before. The fall wiped some $620 billion off the market.
SCRAMBLE TO STOP WATER EVAPORATING
Authorities have spent days desperately trying to prevent the water which is designed to cool the radioactive cores of the reactors from evaporating, which would lead to overheating and the release of dangerous radioactive material into the atmosphere.
Levels of 400 millisieverts per hour had been recorded near the No. 4 reactor, the government said. Exposure to over 100 millisieverts a year is a level which can lead to cancer, according to the World Nuclear Association.
Several embassies advised staff and citizens to leave affected areas in Japan. Tourists cut short vacations and multinational companies either urged staff to leave or said they were considering plans to move outside Tokyo.
German technology companies SAP and Infineon were among those moving staff to safety in the south. SAP said it was evacuating its offices in Tokyo, Osaka and Nagoya and had offered its 1,100 employees and their family members transport to the south, where the company has rented a hotel for staff to work online.
"WHAT THE HELL IS GOING ON?"
Japanese media have became more critical of Kan's handling of the disaster and criticized the government and plant operator Tokyo Electric Power Co. for their failure to provide enough information on the incident.
Kan himself lambasted the operator for taking so long to inform his office about one of the blasts on Tuesday, Kyodo news agency reported.
Kyodo said Kan had ordered TEPCO not to pull employees out of the plant. "The TV reported an explosion. But nothing was said to the premier's office for about an hour," a Kyodo reporter quoted Kan telling power company executives. "What the hell is going on?"
Nuclear radiation is an especially sensitive issue for Japanese following the country's worst human catastrophe -- the U.S. atomic bombs dropped on Hiroshima and Nagasaki in 1945.
There have been a total of four explosions at the plant since it was damaged in last Friday's massive quake and tsunami. The most recent were blasts at reactors Nos. 2 and 4.
Concern now centers on damage to a part of the No.4 reactor building where spent rods were being stored in pools of water outside the containment area, and also to part of the No.2 reactor that helps to cool and trap the majority of cesium, iodine and strontium in its water.
VILLAGES AND TOWNS WIPED OFF THE MAP
The full extent of the destruction from last Friday's 9.0-magnitude earthquake and the tsunami that followed it was becoming clear as rescuers combed through the region north of Tokyo where officials say at least 10,000 people were killed.
Whole villages and towns have been wiped off the map by Friday's wall of water, triggering an international humanitarian effort of epic proportions.
There have been hundreds of aftershocks and more than two dozen are greater than magnitude 6, the size of the earthquake that severely damaged Christchurch, New Zealand last month.
About 850,000 households in the north were still without electricity in near-freezing weather, Tohuku Electric Power Co. said, and the government said at least 1.5 million households lack running water. Tens of thousands of people were missing.
Hiromichi Shirakawa, chief economist for Japan at Credit Suisse, said in a note to clients that the economic loss will likely be around 14-15 trillion yen ($171-183 billion) just to the region hit by the quake and tsunami.
"The earthquake could have great implications on the global economic front," said Andre Bakhos, director of market analytics at Lec Securities in New York. "If you shut down Japan, there could be a global recession."
(Additional reporting by Nathan Layne, Linda sieg, Risa Maeda, and Leika Kihara in Tokyo, Chris Meyers and Kim Kyung-hoon in Sendai, Taiga Uranaka and Ki Joon Kwon in Fukushima, Noel Randewich in San Francisco, and Miyoung Kim in Seoul; Writing by David Fox and Jason Szep; Editing by Dean Yates)