Japan landslide: 20 people missing in Atami city
An emergency taskforce arrives in the area around Atami, which has seen heavy rain.
www.bbc.com
Video on social media showed a torrent of black mud plummeting down from a mountain top and on through the city towards the sea.
Several houses were destroyed or buried.
Kyodo news agency reports that the bodies of what appear to be two victims have been found in the port district.
A witness described a "horrible sound" before he fled to higher ground.
Prime Minister Yoshihide Suga has put together a task force to respond to the disaster and the wider emergency caused by heavy rainfall on the Pacific coastline.
Atami, a popular hot-spring resort in the prefecture of Shizuoka, has had more rainfall in the first three days of July than it usually sees in the whole month. The weather has been similar in neighbouring Kanagawa prefecture.
Japan is a very mountainous and densely populated country and landslides are not unusual, says the BBC's Rupert Wingfield-Hayes, in Tokyo.
But there is growing evidence that climate change is making these sorts of extreme weather events more frequent and more destructive, our correspondent adds.