A series of massive earthquakes have struck north-east Japan, unleashing a 10-metre tsunami that swept buildings, vehicles, crops and debris across swaths of farmland.
The first 8.9 magnitude shock is said to be the biggest to have hit Japan in 140 years, rocking buildings 235 miles (380km) away in Tokyo and sparking fires.
At least five people are known to have died, but amid widespread reports of landslides, floods, collapsed buildings and fires, the death toll is expected to rise.
The quake hit at 2.46pm (5.45am GMT), about 6 miles below sea level and 78 miles off the east coast. It was swiftly followed by five powerful aftershocks of up to 7.1 magnitude. In Tokyo people screamed and grabbed each other's hands as the quake struck. The shock was so powerful it was felt as far away as Beijing.
Television footage showed a 4-metre tsunami sweeping over embankments in Sendai city, bearing cars and houses – some on fire – across farmland, before reversing course and carrying them out to sea. Public broadcaster NHK showed images of a large ship ramming into a breakwater in Kennuma city, Miyagi prefecture.
The quake and tsunami halted air and rail services across large parts of the country. Eight military planes were scrambled to survey the damage as areas along Japan's entire Pacific coast braced for aftershocks and the possibility of more tsunami.
The Pacific tsunami warning centre in Hawaii said a warning was in effect for Japan, Russia, Marcus Island and the Northern Marianas. Tsunami watches have been issued for Guam, Taiwan, the Philippines, Indonesia, Hawaii and the entire western coast of the US and Canada, from the Mexican border to Chignik Bay in Alaska.
The Japanese prime minister, Naoto Kan, promised a quick response as he called an emergency cabinet meeting.
"The earthquake has caused major damage in broad areas in northern Japan," Kan said during an emergency news conference. "Some of the nuclear power plant in the region have automatically shut down, but there is no leakage of radioactive materials to the environment."
The shutdown left 4m homes in and around Tokyo without power.
Kan said he had set up an emergency taskforce to co-ordinate the rescue effort.
"The government will make an all-out effort to ensure the safety of all the people and contain the damage to the minimum," he said.
Junichi Sawada, an official with Japan's fire and disaster management agency, said: "This is a rare, major quake, and damages could quickly rise by the minute."
Fire department officials in Osaki, Miyagi prefecture, said at least 20 people had been injured by falling objects, with some reportedly trapped under debris. At least 10 people were injured when part of a hall roof collapsed in Tokyo, the metropolitan police department said.
All flights were grounded immediately after the quake while officials checked for runway damage. Strong tremors were felt in Tokyo about 30 minutes after the quake. Newsreaders in the capital wore helmets as they gave updates, while office workers rushed out of buildings and on to the streets for safety.
Osamu Akiya, 46, was working at his Tokyo office when the quake hit, sending bookshelves and other items flying and opening up cracks in the wall.
"I've been through many earthquakes, but I've never felt anything like this," he said. "I don't know if we'll be able to get home tonight."
Television footage showed a building on fire in the Odaiba district of Tokyo, although it was not immediately clear if the blaze was connected to the earthquake. Another fire was seen burning out of control at the at Cosmo oil refinery in Ichihara, in Chiba prefecture near Tokyo.
Water levels rose quickly in the coastal town of Miyako in Iwate prefecture, while vehicles, houses and buildings were swept away by the tsunami in Onahama city, Fukushima prefecture.
TV news presenters repeatedly warned people along the Pacific coast to head for higher ground.
The quake is one of several to have struck north-east Japan this week, including one of magnitude 7.3 on Wednesday.
In 1933, a magnitude 8.1 quake in the area killed more than 3,000 people. Last year fishing facilities were damaged by a tsunami caused by a strong quake in Chile.
Japan is one of the most seismically active countries in the world, accounting for about 20% of the world's earthquakes of magnitude 6 or greater.
