Britain "stands ready" to support Japan in any way it can after it was hit by a second devastating earthquake, David Cameron has said.
Rescue missions are under way in the Kumamoto region on the south-western island of Kyushu after a magnitude-7.3 tremor that left at least 22 dead.
It follow a magnitude-6.5 earthquake in Kyushu on Thursday that killed at least ten.
More than 1,500 were injured into the two disasters and hundreds of thousands of people have been left without electricity or water.
Japan's prime minister, Shinzo Abe, said "daytime today is the big test" for rescue efforts as he warned that heavy rain and strong winds could now cause mudslides in the affected areas.
Mr Cameron said the UK was following the situation closely.
The Prime Minister said: "I am deeply saddened by the earthquake in Kumamoto. This second powerful earthquake, following so quickly after the first earthquake on Thursday, has brought further terrible devastation and loss of life. Our thoughts are with all those affected.
"The full extent of the damage will only become clear over the next few days. The UK is following the situation closely and stands ready to support the Japanese response in any way we can."