Urgent action is needed to deliver assistance to hundreds of thousands of Haitian children affected by four storms that have hammered the Caribbean country since August, UNICEF said Tuesday.

"Relief operations are moving towards the post-disaster recovery activities, but pressing humanitarian needs are yet to be met," the United Nations Children's Fund said in a statement.

"Entire parts of the country remain inaccessible by road due to landslides and collapsed bridges," it added, noting that the delivery of humanitarian supplies is depending on sea and air transportation.

More than 425 people have died in Haiti in the wake of major storms Fay, Gustav, Hanna and Ike. The onslaught of treacherous weather triggered mass flooding across the island nation and subsumed much of its rice-growing region under water.

The Haitian government estimates more than 300,000 children still require assistance, according to UNICEF.

More than 400 schools were said to have been damaged by the storms, while others have been converted into shelters for survivors. Children are scheduled to return to school on Oct. 6.

Only three per cent of an appeal for $107 million US has been raised, UNICEF said in its statement. Another $18 million US has reportedly been pledged but not delivered.

The devastation in Gonaives, one of the regions worst hit by the storms, "reminds me of the [2004 Indian Ocean] tsunami when I was in Aceh, [Indonesia], except that this time there is so much mud everywhere that it is hard to see how the people will get rid of it," said Nigel Fisher, president of UNICEF Canada, following a recent trip to the area.

Much of Gonaives, the nation's fourth-largest city, is still flooded and without electricity. Malaria and other water-borne diseases are reportedly beginning to spread.

The UN body said it has already provided 120,000 litres of water, water purification tablets, hygiene kits, blankets and foodstuffs to storm survivors.

With files from the Associated Press