International rescue; Brit teams fly in after quake tragedy 'on massive scale'.
A four-man team from the UK Government and 71 rescue specialists with dogs and heavy equipment arrived shortly after 7am and were due to travel to Port-au-Prince, the capital of Haiti, today, the Department for International Development said.
Haitian prime minister Jean-Max Bellerive said he feared more than 100,000 could have died, although figures were sketchy. The Red Cross said an estimated three million people may need emergency aid.
President Rene Garcia Preval later suggested the death toll was more like 50,000, while a Haitian senator claimed it could be up to half a million.
Britain's International Development Secretary Douglas Alexander said the UK experts were "desperately needed".
"This is a tragedy on a massive scale. Britain is playing its part in the huge international response."
Later he said there were thought to be 32 British nationals living in Port-au-Prince -half of whom had yet to make contact with the UK ambassador to Haiti.
"There are no indications of British casualties,'' he added.
Mr Alexander was to meet with British aid agencies to launch a Disasters Emergency Committee appeal for victims of the quake.
He said: ''My ambassador told me there was a very strange atmosphere in the city today. Many people are not willing to go back into buildings. So there are not just bodies in the streets but people are actually living on the streets at the moment.'' British-based charities also launched appeals to raise money to fund rescue efforts, food, water, shelter and medicines.
The quake hit the Caribbean island state shortly before 5pm local time (9.53pm GMT) on Tuesday, toppling hundreds of buildings in Port-au-Prince.
Seismologists said the impact of the quake measured 7.0 on the Richter scale.
Its epicentre was within 10 miles of the centre of Port-au-Prince, where around one million people live.
The chief of the UN mission to Haiti, Hedi Annabi, was among the dead.
More than 100 people were missing at the organisation's collapsed HQ and another 40 UN staff were unaccounted for in other buildings. Sixteen UN peacekeepers and police are known to have died.
UN Secretary General Ban Ki-Moon urged the international community "to come to Haiti's aid in this hour of need".
He announced the UN would provide 10 million US dollars (pounds 6.2m) for relief from its emergency fund.
US President Barack Obama said American civilian assistance and search and rescue teams would be arriving in Haiti over the next two days.
Prime Minister Gordon Brown said the Government would give "support to help the people of Haiti recover from this devastating event."
Foreign minister Baroness Kinnock said the Foreign Office was ''working hard to locate and contact British nationals in the country'' but there were so far no reports of British casualties.