Daybreak revealed the full extent of the damage from Friday's 8.9 magnitude earthquake - the strongest in Japan since records began - and the 10-metre high tsunami it sent surging into cities and villages, sweeping away everything in its path.
At least 402 people have been killed but Japan's Jiji Press News agency said police and other data showed that the total number of quake dead and missing topped 1,000.
Adding to the nation's woes, authorities issued an atomic alert after the quake damaged cooling systems at two nuclear power plants.
Thousands of people were evacuated from areas around the No. 1 and No.2 reactors at Fukushima, and authorities were forced to release what they said were small amounts of radioactive steam from both reactors to reduce the pressure.
The aftershock, which the US Geological Survey says hit at a depth of just 24 kilometres, was centred 174 kilometres east-south-east of the tsunami-hit city of Sendai.
Grim updates indicating appalling loss of life keep emerging from along the hard-hit east coast of northern Honshu island, where the monster waves destroyed more than 3,000 homes.