MANILA, Philippines - A fund-raising effort to help millions displaced by two deadly cyclones in the Philippines has fallen US$55 million (S$77 million) short, and more aid is needed, a UN official said Tuesday.

So far, only US$19 million had been committed from the US$74 million the United Nations requested in a "flash appeal" last week, said UN Under-Secretary-General for Humanitarian Affairs John Holmes.

That money is just for relief connected to Tropical Storm Ketsana which hit the Southeast Asian nation on September 26.

But the United Nations will have to ask for more than the US$74 million initially requested after Tropical Storm Parma battered the country from October 3 to 10, said Holmes.

"We will revise it (the sum). We may need to increase it," Holmes told reporters.

"The crisis is by no means over. Indeed, the hard work is just starting," he said.

He would not specify how much money would be needed, saying both the UN and the government were still working together to assess the full damage from Ketsana and Parma.

The storms caused massive flooding in the capital Manila and surrounding areas, huge landslides in the northern mountains and left about 650 dead, civil defence officials said.

Holmes said raising aid and relief funds for this "double disaster" was made more complicated by global financial turmoil and a spate of other disasters in the region which also needed aid money.

Food, shelter and medical care are needed by the more than six million people who Manila said were displaced by the storms, he said.

The country also urgently needs to better prepare itself for more disasters, he added.

Among the threats were diseases that could be spawned by stagnant flood waters that still cover many towns.

"Clearly, there is a major risk of disease," said Holmes, calling for ways to remove the stagnant water rather than waiting for it to recede on its own.

UN resident coordinator Jacqueline Badcock said Holmes would be meeting with the world donor community in the coming days to see how to get more aid.

While the government was already looking at rebuilding, "we have to get through the immediate crisis situation first," she said.