The most-powerful earthquake in Japan's recorded history struck off the country's northeast coast on Friday, leaving hundreds of people dead, injured or missing.

The 8.9-magnitude earthquake triggered a deadly tsunami that washed far inland, swamping towns, sweeping away a train and sparking massive fires that burned through the night.

The exact death toll was not immediately clear, but there were reports that 200 to 300 bodies were found in the northeastern coastal city of Sendai alone. Another 547 are missing and 798 people were injured, police said.

Kaoru Ishikawa, the Japanese ambassador to Canada, told CBC News that officials haven't determined how many people had died after the devastating quake and tsunami.

"We are trying indeed to check what's going on, but unfortunately the scope of the casualties we don't know yet," he said.

Local media are reporting that the death toll is expected to climb and could pass 1,000.

The offshore quake struck at 2:46 p.m. local time at a depth of 24 kilometres about 125 kilometres off the coast, according to the U.S. Geological Survey.

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Massive fires triggered by the quake were burning in many communities, and at least one oil refinery was ablaze, officials said.

A state of emergency was declared near a damaged nuclear power plant, prompting the government to order that about 3,000 people leave the area.

'Enormous damage' reported

Prime Minister Naoto Kan said the disaster caused "major damage" in broad areas in northern Japan.

A massive tsunami sweeps in to engulf a residential area after a powerful earthquake in Natori, Miyagi Prefecture, in northeastern Japan on Friday. Kyodo/Reuters

Japanese officials urged people in affected areas to move to higher ground as the quake-spawned tsunami, which reportedly reached heights of four metres to seven metres, swept towards land.

"There were warnings immediately, telling people to stay away from coastlines and to seek higher ground or to go to the third or fourth floors of the buildings they were in," said Andrew Horvath, a Canadian living in Kyoto.

The tsunami washed over embankments, swamping several coastal communities, with media agency aircraft capturing the devastation on video. The wave knocked down power lines and swept cars, homes and massive islands of debris out to sea.

Buildings collapsed and landslides were reported in several communities along the 2,100-kilometre stretch of coastline.

Japan's coast guard said it was searching for a ship that was swept away from a shipyard and Reuters reported that one train was derailed and another was missing in Miyagi prefecture.

The quake and the aftershocks sparked dozens of fires in towns and cities in the northern prefectures of Fukushima, Sendai, Iwate and Ibaraki.

Some of the dozens of aftershocks were severe — two registered 7.1 and 6.6 in magnitude, according to the USGS.

Police in Sendai also said there was a major explosion at a petrochemical complex in the city, the Australian Broadcasting Corporation reported.

"Our initial assessment indicates that there has already been enormous damage," chief government spokesman Yukio Edano said. "We will make maximum relief effort based on that assessment."

Sayaka Matsumoto, a spokeswoman for the Japanese Red Cross, said emergency teams who were rushing to the scene to provide medical services were using emergency radios to communicate because phone lines were down.

"We will bring a tent, equipment, and doctors and nurses," she said. "We can basically build a clinic in the middle of nowhere."

Ishikawa said steep terrain and rough conditions made it difficult for emergency crews to assess the damage. He said emergency crews and helicopters were dispatched to the hard-hit areas, but he noted that the initial search effort slowed as night fell.

Search and rescue efforts were also slowed by dozens of powerful aftershocks that followed the initial quake.

Nuclear power plant concerns

In the northeast, the Japanese government declared its first-ever state of emergency at a nuclear power plant and ordered 3,000 residents to leave the area after the quake caused a problem in the plant's cooling system.

Radiation in a reactor at the plant rose to 1,000 times normal, Japan's nuclear safety agency said, and some radiation was reported to have seeped out of the reactor.

Japan's nuclear safety agency said pressure inside the reactor at the Fukushima No. 1 power plant has risen to 1.5 times the level considered normal.

Plant workers were scrambling to restore the cooling water supply at the plant but there is no prospect for an immediate success, The Associated Press reported. The U.S. is rushing coolant to Japan.

The International Atomic Energy Agency said Japanese authorities also reported a fire at the Onagawa nuclear plant, a fire that has since been extinguished.

"They say Onagawa, Fukushima-Daini and Tokai nuclear power plants were also shut down automatically, and no radiation release has been detected," the IAEA said in a statement posted online.

Tokyo rattled

The violent tremors reached as far as Tokyo, hundreds of kilometres from the quake's epicentre.

TV footage showed a large building on fire and billowing smoke in the Odaiba district of Tokyo. The tremor bent the upper tip of the iconic Tokyo Tower, a 333-metre steel structure inspired by the Eiffel Tower in Paris.

"In my apartment building, which is a three-storey building, it was shaking back and forth," said Craig Dale, a Tokyo-based freelance reporter.

Ian MacDougall, a Canadian translator living in Tokyo, said the quake came on "a lot harder and faster than they usually do."

"The kind of rattling of furniture and creaking of the house was different — this was a different order of magnitude."

Dale said some metro lines in Tokyo were back up and running but there were still major delays.

Sadia Kaenzig of the International Red Cross said more than four million households were without power.

Houses lie flattened in Iwaki, Japan, on Friday. Kyodo/Reuters

U.S. President Barack Obama sent his condolences to the people affected by the quake and the tsunami, saying the U.S. "stands ready to help" the Japanese.

Prime Minister Stephen Harper also offered his condolences and said Canada will "stand by the people of Japan during this difficult moment."

He said Canadian officials are working with Japanese authorities to try to determine whether any Canadians were injured by the earthquake or the tsunami.

Tsunami warnings and advisories were issued in dozens of nations in the Pacific basin after the quake, including the west coasts of South America, the United States and Canada.

Many of the advisories were later lifted but the tsunami advisory for British Columbia remained in effect Friday morning, even as the initial effects of the Japan earthquake appeared to pass the province's coastline without apparent incident.

Fatal quakes

Japan's worst previous quake occurred in 1923 in Kanto, an 8.3 magnitude temblor that killed 143,000 people, according to the USGS.

In later decades, Japan brought in strict building codes designed to minimize earthquake damage and loss of life, restricting the harm from seismic activity.

Still, a 7.2 magnitude quake in Kobe city in 1996 killed 6,400 people.

Japan lies on the "Ring of Fire" — an arc of earthquake and volcanic zones stretching around the Pacific where about 90 per cent of the world's quakes occur, including the one that triggered the Dec. 26, 2004, Indian Ocean tsunami that killed an estimated 230,000 people in 12 nations.

With files from The Associated Press