Torn up and terrified by a disaster that keeps getting worse, Japan has been transformed in just a few days from one of the world’s most comfortable countries into one of its most distressed.

Thousands of people along the northeastern coast of Asia’s richest nation are dead, and tens of thousands have gone days with little food, little water and almost no heat. Their towns have been demolished, with nothing in their place but soggy fields of scraps.

An escalating nuclear emergency has caused panic among stock traders, triggered evacuation orders from foreign companies and generated a deep sense of unease among millions of residents concerned about radiation exposure.

One catastrophe alone would have been overwhelming. But since Friday, Japan has been hit by a 9.0-magnitude earthquake, a shoreline-crushing tsunami and an evolving crisis at the Fukushima Daiichi nuclear power plant. A separate 6.4-magnitude earthquake — not an aftershock, according to the U.S. Geological Survey — struck 55 miles south of Tokyo late Tuesday, shaking buildings, interrupting train service and briefly closing highways.

The pileup of disasters has multiplied the complications. On Tuesday, radiation leakage prompted mass evacuations and a no-fly zone around the Fukushima nuclear facility. Malfunctioning plants have left the country with an energy shortage, leading to power outages at some shelters even as the weather has turned colder. The stock market plunged more than 10 percent Tuesday.

Across the upper half of Japan’s main Honshu Island, life is either in tatters or at a standstill. Energy-cutting efforts by companies and train lines have slowed the pace of business in greater Tokyo, where roughly a quarter of the country’s population is concentrated. Many people are choosing to stay indoors or are leaving only to buy groceries, on the thin chance that there is a stock of milk or rice.

Along the coast, the damage is more acute, and 6,000 people are officially confirmed as dead or missing, according to the police tally. The latest death toll stands at 3,373. Officials in Miyagi prefecture estimate that at least 10,000 of its 2.3 million citizens were killed by the quake and tsunami.

Hospitals, short of medicine and supplies, are struggling to treat seriously injured or ill patients, and overwhelmed local officials have not been able to secure enough space for morgues and coffins. The continuing blackout has made it impossible to create dry ice to pack bodies. About 500,000 people in Japan have been displaced or evacuated.

Amid the turmoil, Prime Minister Naoto Kan has asked for calm, and there has been no mass exodus of Tokyo residents to more western cities such as Osaka and Kyoto. Bullet trains have available seats, and rail platforms are no more crowded than usual.

Still, some foreign companies and embassies have decided that parts of Japan have become too dangerous. Austria relocated its embassy from Tokyo to Osaka. The Chinese Embassy in Tokyo said it was evacuating its citizens from the regions closest to Fukushima. Foreign airlines in China and Taiwan said they will cut back on flights.

Snaking lines formed at Tokyo’s Narita and Haneda airports Tuesday afternoon as foreigners packed the ticket counters, hoping to catch a flight far away from Japan and the threat of radiation poisoning.

Hours or days before their flights were scheduled to leave, thousands gathered at Haneda airport, even though they had been told several times that no earlier flights were available.

“Anywhere but here,” said Maria Sumner, a 23-year-old from Washington, Mo., who was headed to San Francisco on Tuesday after a deluge of worried e-mails from family and friends. “It just got to be a little too much.”

Just hours earlier, the nation watched Kan deliver a televised address. He wore a durable blue work jacket. “Please listen to my message calmly,” he said, before he summarily explained that radiation had spread from malfunctioning reactors at Fukushima Daiichi into the environment. Readings in the nearby area suggested a very high risk, he said.

The government ordered several hundred people who had ignored an earlier evacuation notice and remained within 12.5 miles of the plant to get out. It asked those outside that radius but within 19 miles to stay indoors. Those outside that radius — including the 13 million residents of Tokyo, 150 miles to the south — wondered whether to trust what little information they received from the government, whose top spokesman said those in the capital would be safe.

Meanwhile, the Nikkei 225 recorded one of its largest-ever drops, closing at 8605.15 — down 10.5 percent. Coupled with Monday’s 6.2 percent drop, the index plummeted nearly 17 percent in the first two business days since the catastrophe, though it recovered a bit in early trading Wednesday.

Many of the losses were due to a rapid sell-off that occurred just as Kan warned about the radiation risks.

At an earlier news conference Tuesday, four officials from the Tokyo Electric Power Co., which operates the nuclear plant, offered almost no information about the damage that occurred during the explosion, or its implications.

“What has happened in the stock market reflects the amount of uncertainty — the different rumors that are floating around,” said Edwin Merner, a 30-year resident of Tokyo and president of Atlantis Investment Research, “a certain panic thinking that is going on. I think the main thing is, people just don’t know. And they don’t necessarily trust the information they have been hearing.”

Staff writer Rick Maese and special correspondent Akiko Yamamoto contributed to this report.