Hundreds of thousands of people in the southern Philippines are in dire need of help one month after devastating floods, but a global appeal for aid has fallen well short of its target, the UN said Tuesday.

The official death toll from tropical storm Washi, which destroyed entire villages built on sandbars and on riverbanks in two port cities on December 16, is 1,259, but many more are believed to have been buried or washed out to sea.

Meanwhile, another 222,000 survivors are struggling after losing their homes and need help, according to the United Nations Humanitarian Coordinator for the Philippines, Jacqui Badcock.

She said a "flash appeal" issued immediately after the disaster to help survivors for $28 million had attracted only $7.4 million.

"It (the shortfall) doesn't stop us from being active but there are many projects we could expand if we got more resources," Badcock told AFP.

"We could build more latrines, put up more temporary shelters."

Badcock said 26,000 of the survivors were in overcrowded evacuation centres in Cagayan de Oro and Iligan cities, while another 200,000 were living in makeshift shelters or with relatives.

Many of the evacuation centres are gymnasiums and schoolhouses, but this has caused problems with students having returned to classes after the Christmas holidays, according to Badcock.

"Right now, they are trying to strike balances in the evacuation centres where children are given lessons while families wait outside," she said.

Another growing concern is the psychological counselling that survivors of the floods need, she added.

Victoriano Kapayo, 30, buried two drowned children after the flood, and he said he was haunted by a third child, a six-year-old daughter, who remains missing.

"I feel she is still alive. I always see her in my dreams," he said at the gymnasium where he and his wife were being sheltered.