At least two people are dead and about 20 are missing after a mudslide swept away homes and cars in a resort town southwest of Tokyo, Japanese officials said.
Prime minister Yoshihide Suga told reporters 19 people had been rescued, and 130 homes damaged in Atami.
Speaking after an emergency cabinet meeting, he added two people were dead and two were injured but more were feared missing.
Earlier, disaster officials said 20 were unaccounted for, but warned the number may rise.
Mr Suga said: “The area is still having heavy rainfall, but arduous rescue efforts will continue. Please act as quickly as you can to stay safe.”
Troops, firefighters and other rescue workers, backed by three coast guard ships, were working to clear the mud from the streets of Atami and reach those believed to be trapped or carried away.
The deluge crashed down a mountainside into rows of houses following heavy rains that began several days ago.
Bystanders, their gasps of horror audible, caught the scene on cell phone video. Witnesses said they heard a giant roar and then watched helplessly as homes were gobbled up by the muddy waves.
The two people confirmed dead, both women, had been swept to the sea and were found by the coast guard, said Shizuoka prefecture official Tatsushi Ueda, adding 121 people in Atami had been evacuated.
Prime Minister Yoshihide Suga has set up a task force for the rescue effort.
Atami is a quaint seaside resort area in Shizuoka prefecture, about 100 kilometres (60 miles) southwest of Tokyo.
The area that was hit by the mudslide, Izusan, includes hot springs, residential areas, shopping streets and a famous shrine.