A huge tidal surge has been captured on video flowing up a river in Japan following the country’s latest earthquake.

The surge up the Sunaoshu River in the city of Tagajo - which was devastated by the 2011 tsunami - was caused by a 7.4 quake that hit early on Tuesday morning.

There were no immediate reports of deaths or serious injuries.

The epicentre was off the coast of Fukushima prefecture at a depth of about 10km (6 miles), the Japan Meteorological Agency (JMA) said.

A wave of up to 1.4 metres (4.5 ft) high was recorded at Sendai, about 70km (45 miles) north of Fukushima, with smaller waves hitting ports elsewhere along the coast, public broadcaster NHK said.

Television footage showed ships moving out to sea from harbours as tsunami warnings wailed after alerts of waves of up to 3 metres (10 feet) were issued.

"We saw high waves but nothing that went over the tidal barriers," a man in the city of Iwaki told NTV television network.

Aerial footage showed tsunami waves flowing up rivers in some areas, and some fishing boats were overturned in the port of Higashi-Matsushima before the JMA lifted its warnings.

The US Geological Survey measured Tuesday's quake at magnitude 6.9, down from an initial 7.3.

All Japan's nuclear power plants in the area have been shut down in the wake of the March 2011 disaster, which knocked out cooling systems at Tokyo Electric Power Co's Fukushima Daiichi nuclear plant, causing reactors to melt down and spew radiation into the air, soil and sea.

The cooling system for a storage pool for spent nuclear fuel at the reactor at its Fukushima Daini Plant was initially halted on Tuesday, said a spokeswoman for Tokyo Electric Power, known as Tepco, but was restarted soon after.

Only two reactors are operating in Japan, both in the southwest. Nuclear plants require cooling systems to remain operational even when shutdown in order to keep spent fuel cool.

Offshore earthquake sparks Japan tsunami warning

Tohoku Electric Power Co said there was no damage to its Onagawa nuclear plant, while the Kyodo news agency reported there to be no irregularities at the Tokai Daini nuclear plant in Ibaraki prefecture.

Japanese Minister for Disaster Management Jun Matsumoto told reporters there had been no reports of significant injuries. One woman suffered cuts to her head from falling dishes, Kyodo reported, citing fire department officials.

Earthquakes are common in Japan, one of the world's most seismically active areas. Japan accounts for about 20 per cent of the world's earthquakes of magnitude 6 or greater.

The March 11, 2011 quake was magnitude 9, the strongest ever recorded in Japan. The massive tsunami it generated knocked out the Fukushima plant, causing the worst nuclear crisis since Chernobyl a quarter of a century earlier.

Systems have been updated since the 2011 disaster to spread warnings more quickly, said Tsunetaka Omine, head of the Disaster Management Division in Iwaki, a city in Fukushima prefecture.

Previously, there were complicated directions on where to evacuate. "But now, we basically just tell people to head away from the sea, to the highest possible ground," Mr Omine said.

Authorities now also send tsunami warnings to every mobile phone in the area and broadcast on local radio.

In pictures: Japan earthquakes Show all 20 1 /20 In pictures: Japan earthquakes In pictures: Japan earthquakes In pictures: Japan earthquakes Rescuers check the damage area caused by earthquakes in Minamiaso, Kumamoto prefecture AP In pictures: Japan earthquakes Policemen search for survivors at a landslide site after earthquakes in Minami-Aso, Kumamoto prefecture Getty Images In pictures: Japan earthquakes A search operation for missing persons is conducted around an area of mountain lodges which were buried in a landslide caused by earthquakes in Minamiaso, Kumamoto prefecture AP In pictures: Japan earthquakes Villagers gather in an evacuation center following a series of earthquakes in Minami Aso EPA In pictures: Japan earthquakes A scarred mountainside following a major landslide caused by a series of earthquakes in Minami Aso EPA In pictures: Japan earthquakes Japan Ground Self-Defense Force soldiers conduct search and rescue operations at an apartment which collapsed following an earthquake in Minamiaso town Reuters In pictures: Japan earthquakes A resident walks past collapsed houses in Mashiki AP In pictures: Japan earthquakes A landslide is seen after the earthquake in Minamiaso AP In pictures: Japan earthquakes Rescue workers from Japan's Ground Self-Defense Force dig a vehicle out from mud at a landslide site in Minamiaso EPA In pictures: Japan earthquakes Rescuers guide dogs to search for victims buried in a landslide due to the recent earthquakes in the village of Minami-Aso in Kumamoto prefecture Getty Images In pictures: Japan earthquakes A local resident rests with a pet dog at an evacuation center after an earthquake in Mashiki town Reuters In pictures: Japan earthquakes Collapsed houses caused by an earthquake are seen in Mashiki town Reuters In pictures: Japan earthquakes A shop clerk cleans broken wine bottles following an earthquake in Kumamoto city Getty Images In pictures: Japan earthquakes A woman cleans up in front of her collapsed house in the town of Mashiki, Kumamoto prefecture Getty Images In pictures: Japan earthquakes Resident Nobuyuki Morita (R) and his wife look around a room in their house in the town of Mashiki, Kumamoto prefecture Getty Images In pictures: Japan earthquakes Policemen search for missing people in a damaged neighbourhood following twin earthquakes in Mashiki Getty Images In pictures: Japan earthquakes Local residents evacuate from the town centre in Kumamoto Getty Images In pictures: Japan earthquakes Rescue team saved a man from his house buried alive Getty Images In pictures: Japan earthquakes An eight-month-old baby is carried away by rescue workers after being rescued from her collapsed home caused by an earthquake in Mashiki town Reuters

Teacher Kathy Krauth, who was staying in a traditional Japanese inn on the coast in the city of Ofunato with a dozen international high school students on a study tour, said the shaking began just seconds after a quake alarm on her phone went off.

"I felt like the lessons of 3-11 were really taken to heart," said Ms Krauth, who teaches a class on the March 2011 disaster and its aftermath. "The feeling was, we just don't know, but we're going to be as cautious as we can."

Nissan said it would suspend work at its engine factory in Fukushima at least until the latest tsunami warning was lifted. A spokesman said there were no injuries or damage at the plant, which was badly damaged in the 2011 disaster.

Toyota said all its factories in northeastern Japan were operating as usual.

Japan's famous Shinkansen bullet trains were halted along one stretch of track and some other train lines were also stopped.

Japanese financial markets were little affected, with the Nikkei 225 index closing up 0.3 percent and the yen steady against the US dollar.