A team of UK search and rescue specialists and medics was due to join the massive relief mission in tsunami-ravaged Japan today amid the continuing threat of a catastrophic nuclear meltdown.
At least 1,300 people are believed to have been killed by the wall of water, but thousands more are missing - including 10,000 from the Japanese coastal town of Minamisanriku.
Strong aftershocks have rocked the north-east area of the island nation, with one measuring 6.2 on the Richter scale striking this morning, further hindering the multi-national rescue effort.
Meanwhile, Japan's nuclear safety agency said the cooling system of a third nuclear reactor at the Fukushima nuclear plant had failed, with experts constantly monitoring levels of radioactivity in the quarantined area.
The Foreign Office said there were currently no reports of British casualties following Friday's magnitude 8.9 earthquake and ensuing 20ft tsunami that swallowed everything in its path - from houses and cars to trains and ships.
However, it was reported that the British embassy in Tokyo has a "long list" of people unaccounted for.
The UK emergency team organised by the Department for International Development (DfID) set off on board a private charter plane from Manchester yesterday after Foreign Secretary William Hague confirmed Japan requested assistance.
It is made up of 63 UK fire service search and rescue specialists, two rescue dogs and a medical support team drawn from Lancashire, Lincolnshire, Greater Manchester, West Sussex, Kent, West Midlands, Mid West Wales, Hertfordshire and Cheshire.
A spokesman said they are expected to land this morning and will immediately join the international search for survivors, providing relief for Japan's own rescue teams.
The group took 11 tonnes of specialist rescue equipment, including heavy lifting and cutting gear in a bid to save the lives of people still trapped in the debris.
Members of the team have recently returned from the earthquake zone in Christchurch, New Zealand, and have previously been deployed to Haiti and Indonesia.
Japan's prime minister Naoto Kan said 50,000 troops have joined rescue and recovery efforts, trying to reach devastated towns and villages along hundreds of miles of coast by boats and helicopters.
Dozens of countries also offered help, with US President Barack Obama pledging assistance. He said one US aircraft carrier was already in Japan and a second was on its way.
The Japanese earthquake was 8,000 times more powerful than the one which devastated Christchurch, making it one of the largest ever recorded.
More than 215,000 people are living in 1,350 temporary shelters in five prefectures, or states, the national police agency said.
Since the quake, more than one million households have not had water, mostly concentrated in the north east. Some four million buildings were without power.
Around 170,000 people have been evacuated from a 12-mile radius around the Fukushima number one nuclear plant, which was rocked by an aftershock-induced explosion yesterday.
Japan's government spokesman said the blast destroyed a building which houses a nuclear reactor, but the reactor itself escaped unscathed.
As a precaution, officials pumped seawater into the reactor, which has seen the build up of pressure and heat since the double natural disaster caused its cooling system to fail.
However, hours after the explosion the cooling system of a third reactor at the plant failed, prompting renewed fears of overheating.
Mr Hague said: "We are all appalled by the scenes of devastation, by the heavy loss of life, by the destruction we have all witnessed on our television screens.
"I think all over the world, people's hearts go out to the people of Japan.
"I spoke to the Japanese foreign minister today to convey our condolences, and also our offer of help."
The Foreign Secretary said the Government was "concerned" about British citizens who may have been in the affected area, particularly in north eastern Japan".
The department has sent a team of 18 specialist consular response staff to supplement embassy workers in Japan, and further groups are on standby in the US.
The Foreign Office has established a crisis unit and set up a helpline for UK nationals in Japan and their relatives back home. That number is +44 (0)20 7008 0000. So far, it has taken more than 1,200 phone calls.