(Reuters) - Workers were ordered to withdraw briefly from a stricken Japanese nuclear power plant on Wednesday after radiation levels surged, Kyodo news reported, a development that suggested the crisis was spiraling out of control.
Just hours earlier another fire broke out at the earthquake-crippled plant, which has sent low levels of radiation wafting into Tokyo in the past 24 hours, triggering both fear in the capital and international alarm.
The workers were allowed back into the plant after almost an hour when the radiation levels had fallen.
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 last 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 Authorities had withdrawn 750 workers on Tuesday, leaving only 50.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.