Strong aftershocks have continued to hit Japan two days after 24 people died in the country's deadliest earthquake in almost a decade.
The clear-up has begun in Niigata
No fatalities were reported after the latest quake, which measured 5.6 in magnitude and hit on Monday morning.
Rescuers are still looking for people missing after Saturday's quakes, the largest of which was of magnitude 6.8.
Thousands of people spent their second night in emergency shelters, fearful of returning to unstable buildings.
More than 2,000 people were injured and local hospitals say they have been overwhelmed by the number of casualties.
The most devastating quake was centred in Niigata, 260km (160 miles) north of Tokyo.
Much of the affected region is still without power, and authorities warn there is a desperate need for food and water supplies.
The Japanese meteorological agency has warned that more quakes are likely in the near future, and has also forecast several days of heavy rain.
The weekend's events follow a record 10 typhoons to hit Japan this
year, including one that killed at least 80 people last week.
Military helicopters have joined in attempts to reach isolated rural villages cut off by landslides caused by Saturday's quakes.
Rescue efforts have been hampered by widespread power cuts, blocked roads and collapsed bridges.
"I have no food. I have nothing to drink. I have no change of
clothes for my children," one young woman told Reuters news agency after being rescued.
Monday's newspapers carried horrific accounts of the quakes.
Relatives could hear the screams of a 12-year-old girl trapped under her
collapsed second-floor bedroom, according to the Asahi Shimbun.
She perished along with her 64-year-old grandfather who was also buried under the debris.
Prime Minister Junichiro Koizumi told officials to make the "utmost efforts to rescue victims and collect information related to the earthquake", a news report said.
Thousands of people spent the night at evacuation centres
Officials said nearly 100,000 people had sought refuge at local gymnasiums and public buildings across north-west Japan on Sunday night, for fear of further earthquakes.
Others slept in the open air or in their cars, in some cases in temperatures below -10C.
"There has been big damage to lifelines of electricity, gas
and water and many people are at evacuation centres, unable to go
home," Chief Cabinet Secretary Hiroyki Hosoda told Reuters news agency.
Several aftershocks were felt through the night, but the largest was a 5.6 magnitude quake which hit just after dawn on Monday.
No further deaths were caused by these aftershocks, but buildings swayed and there were fears that the area's infrastructure would suffer even more damage.
Many houses, roads and bridges had already been damaged or destroyed over the weekend.
A bullet train was derailed and two tunnels collapsed along the Tokyo-Niigata highway.
Tokyo stocks fell sharply on Monday morning due to economic jitters following the weekend's events.