Scale of damage to roads and poor weather hamper relief efforts, three days after quake off Noto Peninsula.
At least 78 people have been confirmed dead and 330 injured since the magnitude 7.6 earthquake off the Noto Peninsula on January 1, according to local authorities.
On Thursday, officials published a list of 51 people from three cities whose whereabouts could not be confirmed.
More than a dozen communities have been cut off.
Soldiers, firefighters and police officers from across Japan are searching through collapsed wooden houses and toppled commercial buildings for signs of life. Experts say the first three days are especially critical because the prospects for survival drop sharply after that.
“This is a very difficult situation. But from the viewpoint of protecting lives, I ask that you make every effort to save and rescue as many lives as possible by this evening, when the critical 72 hours of the disaster will have passed,” Prime Minister Fumio Kishida said at a government meeting on Thursday.
He announced that the number of troops dispatched to the area for rescue operations was being increased from about 1,000 to 4,600.
The narrowness of the hard-hit Noto Peninsula has added to the challenges in reaching some communities. Water, power and mobile phone services were still down in some areas.
There have been nearly 600 aftershocks since the main quake, raising fears of landslides with forecasts of rain adding to the risk.
Naomi Gonno said she and her children got out of their house just as it came crashing down.
Her children were screaming for their grandmother, and Gonno saw that her mother was trapped under the smashed house, with only her hand visible. She was able to squeeze her way out through a tiny space, Gonno said.
“I can’t believe we’re still alive,” she said. “We are living in fear.”
No water, power
In Wajima, where a massive fire ripped through parts of the port and the district surrounding it, people queued for water and food.
The quake buckled and tore apart roads, making it even more difficult to access the hardest-hit areas.
“Compared to other disasters, the road situation into Wajima is very bad. I feel it’s taking longer than usual for assistance to arrive,” Shunsaku Kohriki, a medical worker, told the Reuters news agency.
“I think, realistically speaking, the evacuees will have to live in really tough conditions for a while yet.”
The full extent of the damage and casualties remains unclear four days after the deadliest quake in Japan since at least 2016.
All the deaths have been reported near the epicentre of the quake in Ishikawa prefecture. More than 33,000 people have evacuated from their homes and about 100,000 houses have no water supply, according to officials in the area.
Four of the world’s tectonic plates meet in Japan making the country particularly prone to earthquakes.
It experiences hundreds of tremors every year, but most cause little to no damage.
Earthquakes have hit the Noto region with intensifying strength and frequency over the past five years.
In 2011, Japan’s northeast was hit by one of the most powerful earthquakes ever recorded.
The magnitude 9.0 undersea earthquake triggered a massive tsunami that wiped out entire communities and triggered a meltdown at the Fukushima nuclear plant. At least 18,500 people were killed.