SENDAI, JAPAN — Japan worked against the clock on Tuesday to avert nuclear fallout, as relief workers cranked up their searches for survivors of last week’s massive and deadly earthquake and tsunami.

The Asian economic powerhouse reeled as the death toll spiked to 3,373 and the stock market plummeted for a second straight day — a 10 percent drop this time — during what Japanese Prime Minister Naoto Kan said was the country’s worst crisis since World War II — when American jets dropped nuclear weapons on Hiroshima and Nagasaki.

Shell-shocked people huddled in cramped shelters, grieved over lost loved ones, and worried about missing next of kin lost throughout villages and towns inundated by the powerful tsunami waves spawned by the 9.0 magnitude quake off the east coast of Honshu on Friday.