Fukushima - Japan scrambled to avert a meltdown at a stricken nuclear plant on Monday after a hydrogen explosion at one reactor and exposure of fuel rods at another, just days after a devastating earthquake and tsunami that killed at least 10 000 people.
Roads and rail, power and ports have been crippled across much of Japan's northeast and estimates of the cost of the multiple disasters have leapt to as much as $170bn. Analysts said the economy could even tip back into recession.
Japanese stocks closed down more than 7.5%, wiping $287bn off market capitalization in the biggest fall since the height of the global financial crisis in 2008.
Rescue workers combed the tsunami-battered region north of Tokyo for survivors and struggled to care for millions of people without power and water in what Prime Minister Naoto Kan has dubbed his country's worst crisis since World War Two.
Officials say at least 10 000 people were likely killed in the 8.9-magnitude earthquake and tsunami that followed it. Kyodo news agency reported that 2 000 bodies had been found on Monday in two coastal towns alone.
"It's a scene from hell, absolutely nightmarish," said Patrick Fuller of the International Red Cross Federation from the northeastern coastal town of Otsuchi.
"The situation here is just beyond belief, almost everything has been flattened. The government is saying that 9 500 people, more than half of the population could have died and I do fear the worst."
The big fear at the Fukushima nuclear complex, 240 km (150 miles) north of Tokyo, is of a major radiation leak. The complex has already seen explosions at two of its reactors on Saturday and on Monday, which sent a huge plume of smoke billowing above the plant.
The nuclear accident, the worst since the Chernobyl disaster in the Ukraine in 1986, sparked criticism that authorities were ill-prepared and the threat that could pose to the country's nuclear power industry.
Jiji news agency said fuel rods at the No. 2 reactor had been entirely exposed and a fuel rod meltdown could not be ruled out. The plant operator confirmed there was little water left in the reactor, adding that the fuel rods may have been exposed.
The rods have now been partially covered by sea water, the reactor's operator said.
There were earlier partial meltdowns of the fuel rods at both the No. 1 and the No. 3 reactors, where the explosions had occurred.
A meltdown raises the risk of damage to the reactor vessel and a possible radioactive leak. Levels of cooling sea water around the reactor core had been reported as falling earlier in the day. Jiji said the pump had run out of fuel.
Crucially, officials said the thick walls around the radioactive cores of the damaged reactors appeared to be intact after the earlier hydrogen blast.
But the government warned those still in the 20-km (13-mile) evacuation zone to stay indoors. The plant operator, Tokyo Electric Power Co (TEPCO), said 11 people had been injured in the blast.