Japan struggled yesterday to avert a nuclear disaster and care for millions of people without power or water three days after an earthquake and tsunami killed an estimated 10,000 people or more in the nation’s darkest hour since World War II.

The world’s third-largest economy opened for business later in the day, a badly wounded nation that has seen whole villages and towns wiped off the map by a wall of water, leaving in its wake an international humanitarian effort of epic proportion.

Officials have been working desperately to stop fuel rods in the damaged reactors from overheating. If they fail, the containers that house the core could melt, or even explode, releasing radioactive material into the atmosphere.

The most urgent crisis centers on the Fukushima Daiichi complex, where all three reactors are threatening to overheat, and where authorities say they have been forced to release radioactive steam into the air.

“Radiation has been released in the air, but there are no reports that a large amount was released,” Prime Minister Kan said.

The nuclear accident has sparked criticism that authorities were ill-prepared for such a quake and the threat that one could pose to the country’s nuclear power industry.

Economic impact to be lasting

A triple blow of earthquake, tsunami and one of Japan’s worst nuclear accidents is set to damage the world’s third-largest economy, possibly more deeply and for longer than initially expected.

Power outages and possible tax increases are likely to hurt companies and households. Rolling blackouts will start today, affecting businesses and households as the country grapples with the crisis.

“Power supply is a critical factor,” said Michala Marcussen, head of global economics at Societe Generale. “If power production output is damaged in a sustainable fashion, that could have a durable impact on the economy.”

The world reaches out in solidarity

GENEVA – With foreign teams helping local rescuers to seek survivors from Japan’s quake and tsunami, countries offered further aid from field hospitals to atomic physicists to address an unfolding nuclear crisis.

Firefighters, sniffer dogs, clothing and food have been proposed in an outpouring of solidarity with Japan, with offers pouring in from nearly 70 countries, the U.N. reports.

Even the poor southern Afghan city of Kandahar announced it was donating $50,000 to the “brothers and sisters” of Japan.

A dozen countries have now deployed rescue teams following Japan’s request, including workers and dogs from Australia, China and the United States, the United Nations said. Seven senior U.N. disaster-relief officials arrived yesterday to help coordinate aid.