Compiled from news reports
An explosion shook a quake-damaged Japanese nuclear power plant Monday but the reactor was apparently not breached, the chief government spokesman Yukio Edano said.
Edano, citing information from the plant operator TEPCO, said the reactor container was likely undamaged and there was a low possibility of major radiation.
Eleven workers were injured.
Japan's nuclear safety agency said the blast, at the number 3 reactor of the Fukushima No. 1 plant, was believed to be caused by hydrogen.
A hydrogen explosion had hit the number 1 reactor at the same plant on Saturday, a day after an earthquake and tsunami devastated the northeast coast.
Authorities have declared an evacuation zone within a 20 km (12 mile) radius of the plant and evacuated 210,000 people.
"We have strongly advised all the people still within the evacuation area to go inside nearby facilities," said nuclear safety agency spokesman Ryo Miyake.
Some 746 people -- patients, elderly people and care workers at three hospitals and nursing homes -- remained within the 20 km area Monday. A Fukushima official said 311 had so far been moved out.
The colossal 8.9-magnitude tremor sent waves of mud and debris racing over towns and farming land in Japan's northeast, destroying all before it and leaving the coast a swampy wasteland.
In the small port town of Minamisanriku alone some 10,000 people were unaccounted for ― more than half the population of the town, which was practically erased, public broadcaster NHK reported.
The police chief in Miyagi prefecture ― where Minamisanriku is situated ― said the death toll was certain to exceed 10,000 in his district alone.
As the world's third-largest economy struggled to assess the full extent of what Prime Minister Naoto Kan called an "unprecedented national disaster", groups of hundreds of bodies were being found along the shattered coastline.
"We have received a preliminary report that more than 200 bodies were found in the city of Higashimatsushima," a National Police Agency spokesman said in the latest find on Sunday.
Edano said at least 1,000 people were believed to have lost their lives, and police said more than 215,000 people were huddled in emergency shelters.
In the city of Fukushima, about 80 kilometers (50 miles) northwest of the stricken plant, AFP reporters saw panic buying at supermarkets and said petrol stations had run dry.
In Minamisoma town, which was virtually obliterated by the tsunami's black tide of mud and debris, an AFP reporter saw fire volunteers collecting bodies found in the twisted wreckage of what had once been a residential area.
An elderly woman wrapped in a blanket tearfully recalled how she and her husband were evacuated from Kesennuma town, another fishing port which the tsunami swept through.
"I was trying to escape with my husband, but water quickly emerged against us and forced us to run up to the second story of a house of people we don't even know at all," she told NHK.
"Water still came up to the second floor, and before our eyes, the house's owner and his daughter were flushed away. We couldn't do anything. Nothing."
The sheer power of the water tossed cars like small toys, upturned lorries that now litter the roads and left shipping containers piled up along the shore.
In Sendai city, where the haunting drone of tsunami sirens had echoed into the night, a hospital used generators to keep its lights blazing, drawing in wearied survivors, but supplies of food and fuel were fast running out.
"We have asked other hospitals to provide food for us, but transportation itself seems difficult," Sendai Teishin Hospital spokesman Masayoshi Yamamoto told AFP.
The International Atomic Energy Agency said about 200,000 people had so far been evacuated from the area around the two Fukushima plants that house a total of 10 reactors.
Japan's nuclear safety agency rated the incident at four on the international scale of zero to seven. The 1979 Three Mile Island accident in the United States was rated five, while the 1986 Chernobyl disaster was a seven.
After Saturday's blast, which sent smoke billowing into the sky, the government moved to calm growing fears, saying the explosion did not rupture the container surrounding the reactor itself.
Workers doused the stricken No.1 reactor with sea water to try to avert catastrophe, in what US experts warned was an "act of desperation" that, in the worst-case scenario, could foreshadow a much more serious disaster.
The plant's operator said that so much water had evaporated from the number-three reactor that at one stage the top three meters (10 feet) of the fuel rods were exposed to the air, although they were later covered again.
Japan's ambassador to the United States Ichiro Fujisaki told CNN: "There was a partial melt of a fuel rod, melting of fuel rod. There was a part of that... but it was nothing like a whole reactor melting down."
A total of 22 people have been hospitalized after being exposed to radioactivity, although it was not immediately clear to what degree they were exposed and what condition they were in.
Japan committed 100,000 troops ― about 40 percent of the armed forces ― to spearhead a mammoth rescue and recovery effort with hundreds of ships, aircraft and vehicles headed to the Pacific coast area.
"There are so many people who are still isolated and waiting for assistance. This reality is very stark," Defence Minister Toshimi Kitazawa was quoted as saying by Kyodo News.
The world rallied behind the disaster-stricken nation, with offers of help even from Japan's traditional rivals. Despite a territorial row that has soured relations, China sent a team of rescuers who were due to arrive Sunday.
The US aircraft carrier Ronald Reagan reached waters off the northeast coast Sunday, part of a flotilla sent by Japan's close ally which has nearly 50,000 military personnel in the country.
The massive earthquake, one of the largest in recorded history, appears to have shifted the main Japanese island by about eight feet (2.4 meters), the US Geological Survey said.
Two days after it struck about 400 kilometres northeast of Tokyo, aftershocks were still rattling the region, including a strong 6.8 magnitude tremor on Saturday and a 6.3 quake on Sunday.
Japan sits on the "Pacific Ring of Fire", and Tokyo is in one of its most dangerous areas, where three continental plates are slowly grinding against each other, building up enormous seismic pressure.

일본 후쿠시마 제1원자력발전소 3호기가 수소폭발했다고 현지언론이 14일 보도했다.
NHK방송과 교도통신 등 현지언론에 따르면 이날 오전 11시께 후쿠시마 제1원자력발전소 3호기에서 수소폭발이 발생했다. 이 발전소에서는 폭발과 함께 하늘높이 연기가 치솟았다.
후쿠시마 원전은 12일 1호기가 폭발한데 이어 2번째 폭발이다.