Rescue teams and relief supplies arrived in Haiti on Thursday to help drag anyone alive from debris after its capital city was practically flattened by the strongest earthquake in the Caribbean region in more than 200 years.

Iceland's search-and-rescue team arrives in Haitian capital with packages of drinking water.[Xinhua]

The International Monetary Fund (IMF) announced it would provide 100 million dollars very rapidly in emergency financing to Haiti.

"I have asked staff to look into all the possibilities and I am pleased to announce that we are able to make 100 million dollars available very quickly," said IMF Managing Director Dominique Strauss-Kahn at a news conference in Washington.

U.S. President Barack Obama said his country was offering 100 million U.S. dollars in emergency assistance for Haiti after it was jolted by a quake of 7.3 magnitude on Tuesday.

Obama said the first dispatch of U.S. rescue and relief workers were on the ground and at work. A survey team would be missioned to identify priority areas for assistance.

Mexico on Thursday sent its fourth aircraft carrying more than 50 relief workers as well as food and medical supplies.

Mexican President Felipe Calderon had earlier pledged 15 million dollars to help reconstruction in the poverty-stricken country, where one third of its 9 million people was believed to have been affected.

Britain announced a 6.2-million-pound aid package (9.9 million dollars) on Thursday, stressing efforts to save lives in the initial stage of relief work.

"The really pressing requirement in the hours ahead is the capability that we will be offering -- that ability to offer cutting equipment and lifting equipment to get people out from the buildings that have collapsed around them," said British International Development Secretary Douglas Alexander.

The British government said its rescue team arrived in the neighboring Dominican Republic Thursday morning and would reach the Haitian capital Port-au-Prince within the day.

A 50-member Chinese rescue team was among the first to arrive in Port-au-Prince in early Thursday. The Chinese peacekeeping unit in Haiti has mobilized 53 peacekeeping police and more than 400 local people to look for survivors from under the rubble before the rescue team arrived.

Countries including Japan, New Zealand, Singapore, Norway and Canada have also pledged aid to the Caribbean nation.

UN Secretary-General Ban Ki-moon said Thursday that it would take days to get the death toll from the devastating earthquake in Haiti, but the figure was estimated to be "very high."

Mauricio Bustamante, operation coordinator of the International Federation of Red Cross and Red Crescent Societies based in Panama City, said up to 100,000 people might have died in the quake.

At least 36 UN staff members have been confirmed dead in the earthquake, a spokesman for the UN mission in Haiti told reporters.

The top UN humanitarian coordinator gave priority to sending doctors and medical supplies to Haiti.

"The local medical infrastructure is both badly damaged and overwhelmed by the number of injuries," said John Holmes. "It's a top priority to get more doctors there, more medical teams, field hospitals and more medical supplies to make sure we can tackle that problem."

After that, the basic needs are water, food and emergency shelter, added Holmes.

However, damaged infrastructure could impede aid inflows. Haiti's main seaport was surrounded by debris in the water, which could make access difficult, said Holmes.

Port-au-Prince's international airport was reopened on Wednesday, but it was feared the airport might not be able to handle the sudden influx of huge aid cargoes.