The King has sent a message to the emperor of Japan following the series of earthquakes which have left at least 73 people dead.
Charles told Emperor Naruhito he and the Queen were "profoundly saddened to hear of the devastating loss of life and injuries".
He added: "We have been following reports closely and I can only say how deeply we feel for all those who are suffering from the dreadful effects of this horrific tragedy.
"We mourn the many lives cut short and our thoughts are with all those who have lost loved ones.
"We greatly admire the bravery and courage of all those involved in the emergency search and rescue services.
"I know that my Government stands ready to support the people of Japan at this exceptionally difficult time."
The Japanese Prime Minister on Wednesday warned a “critical moment” had been reached in the search for survivors of the series of earthquakes with “many” people still trapped under the rubble.
Rescue workers and canine units continued to urgently sift through wreckage of homes and buildings following the 7.6 magnitude quake that hit Japan’s largest island Honshu on New Year’s Day.
The death toll has risen to 73 with dozens of people still believed trapped under rubble on the Noto peninsula, in the Ishikawa prefecture in central Japan, which was the epicentre of the quake.
The area has been hit by dozens of aftershocks that have hindered the relief effort.
“This is a race against time, and I feel that we are at a critical moment,” Prime Minister Fumio Kishida said.
“We have received reports many people are still waiting for rescue under collapsed buildings.”
The first 72 hours are especially critical following an earthquake, experts say, because the prospects for survival greatly diminish after three days.
Mr Kishida said thousands of rescuers were trying to reach parts of the Noto peninsula. Helicopter surveys showed many fires and widespread damage to buildings and infrastructure. The city of Wajima, on the peninsula’s northern tip, has been cut off from land routes. Water, power and mobile phone services were still down in some areas.
The mayor of the coastal city of Suzu Masuhiro Izumiya said: “Hardly any of the homes are standing. They are either partially or totally destroyed.”
Of the deaths counted so far, 39 were in Wajima, while 23 people died in Suzu, according to Ishikawa prefectural authorities. The other deaths were reported in five neighbouring towns.
More than 300 people have been injured, at least 25 of them seriously.
Weather forecasts warned of heavy rainfall in Ishikawa, leading to worries about landslides and further damage to half-crumbled homes.
Relief officials handed out water, blankets, food and other supplies with temperatures expected to drop to near freezing overnight.
The chief cabinet secretary, Yoshimasa Hayashi, warned people to “be alert” for more earthquakes “of an intensity of up to seven” in the coming week.
