Shirakawa, Japan (CNN) -- Rescuers plucked dazed survivors from collapsed homes, muddy waters and raging fires Saturday, a day after a powerful earthquake tore through Japan and unleashed waves that swallowed entire towns along the coast.
More than 900 were killed and about 700 others were missing Japanese public broadcaster NHK reported. The number is expected to go up as rescuers reach more hard-hit areas.
The 8.9-magnitude quake was centered about 130 kilometers (80 miles) from Sendai, a farming and fishing region battling to stay ahead following decades of brain drain from its youth moving to the capital of Tokyo.
In the nearby city of Shirakawa, rescuers dug through the rubble with heavy machinery to reach 13 neighbors trapped when the earth opened up and swallowed their homes.
Relatives and friends huddled in the cold, watching, praying and waiting. Others wept.
Military choppers flew over the affected areas and plucked people from rooftops. In some cases, rescuers trudged along muddy waters, carrying victims on their backs. Weary, mud-spattered survivors wandered through streets filled with crumpled cars and other debris.
The quake was followed by scores of aftershocks Saturday, including one with a magnitude of 7.1
The original quake was centered 230 miles (370 kilometers) northeast of Tokyo -- and left towns and villages along the eastern coast devastated.
"The earth shook with such ferocity," said Andy Clark, who said he experienced it at the airport outside Tokyo.
"I thought things were coming to an end ... it was simply terrifying."
The quake also disrupted rail service and affected air travel. Flight cancellations left at least 23,000 people stranded in two local airports, Kyodo News Agency said. Flights into and out of both airports resumed Saturday.
Six million households, more than 10% of the total in Japan, were without electricity, said Japan's ambassador to the United States, Ichiro Fujisaki.
"I wasn't scared when it started ... but it just kept going and going," said Michelle Roberts, who lives in central Tokyo. "I won't lie, it was quite scary. But we are all OK. We live on the third floor, so most everything shook and shifted."
Roads in affected areas were jammed as residents -- thousands of whom had spent the night in shelters -- tried to get to their homes in outlying areas. Others flocked to nearby shops to buy supplies.
The Japanese government made a formal request for U.S. aid, including military support, and full planning for deployment is in effect with the U.S. military in Japan taking the lead.
Meanwhile, experts worked to ensure nuclear power plants were safe.
An explosion has been reported near a nuclear plant in northeastern Japan's Fukushima prefecture, Japanese public broadcaster NHK said Saturday, citing the country's nuclear and industrial safety agency.
It was not immediately clear where the explosion is in relation to the Fukushima Daiichi plant, or what caused it.
Earlier Saturday, Japan's nuclear agency said workers were continuing efforts to cool fuel rods at the plant as a small amount of radioactive material escaped into the air.
There was a strong possibility that the small amount of radioactive cesium monitors detected was caused by the melting of a fuel rod at the plant, and engineers were cooling the fuel rods by pumping water around them, the agency said.
The impact of the quake was felt far and wide.
In McKinleyville, California, a wave swept three men into the Pacific Ocean as they were reportedly taking photos of the incoming tsunami waves, according to the U.S. Coast Guard.
Two returned to shore, but one died, officials said.
The tsunami brought waves of nearly 7 feet to a harbor in Maui, authorities said. On the U.S. mainland, wave heights from Alaska to California ranged from less than a foot to more than 8 feet. The highest measurement, 8.1 feet, was at Crescent City, California.
The quake was the latest in a series around Japan this week.
On Wednesday, a 7.2-magnitude earthquake struck off the coast of Honshu, the country's meteorological agency said. Early Thursday, an earthquake with a preliminary magnitude of 6.3 struck off the same coast.
Friday's quake is the strongest earthquake in recorded history to hit Japan, according to U.S. Geologic Survey records that date to 1900.
The world's largest recorded quake took place in Chile on May 22, 1960, with a magnitude of 9.5, the USGS said.