DHAKA (Reuters) - Four days after super cyclone Sidr killed more than 2,400 people in Bangladesh, rescuers were struggling to reach isolated areas along the country's devastated coast and give aid to millions of survivors.

"The tragedy unfolds as we walk through one after another devastated village," said relief operator Mohammad Selim in Bagerhat, one of the worst-hit areas. "Often it looks like we are in a valley of death."

Media reports and the chairman of the Bangladesh Red Crescent Society, Mohammad Abdur Rob, said the death toll had already surpassed 3,000, and was likely to go up. The government put the official toll at 2,471 confirmed dead.

"We are trying to reach all the affected areas on the vast coastline as soon as possible, when we will know how many people have exactly died in the devastation," one government official said.

While it will take several days to determine the number of dead and missing, some 3 million survivors who were either evacuated from the low-lying southern coast or whose homes and villages were destroyed will need support, the government said.

Aid workers fear inadequate supplies of food, drinking water and medicine could lead to outbreaks of disease.

Grieving families begged for clothes to wrap around the bodies of dead relatives for burial. In some areas, they put corpses in mass graves.

Reuters reporters in the affected districts said bodies were being discovered by the hour in the rivers and paddy fields and under piles of debris.

NO PROPER FUNERAL

Cyclone Sidr smashed into the coast of southern Bangladesh late on Thursday with 250 kph (155 mph) winds that whipped up a five-metre (16-foot) tidal surge.

In its wake, dead people and animals floated down rivers and the stench of death filled the air. Relatives tried to identify and bring them ashore, before burying them hurriedly without proper ceremonies.

Military ships and helicopters were trying to reach thousands of people believed stranded on islands in the Bay of Bengal and in coastal areas still cut off by the devastating storm.

Officials in affected areas say the death toll given by the ministry is far below the real numbers. Aid agencies have said the toll could rise beyond 10,000.

"Some 2,000 people have died in my area alone," said Anwar Panchayet in Bagerhat district. A huge effort was under way to get food, drinking water and shelter to the millions affected by the storm, the worst to hit disaster-prone Bangladesh since 1991 when nearly 143,000 people died in a cyclone and the tidal surge it triggered.

A much improved disaster preparedness plan, including storm shelters built all along the coastline since the 1991 storm, has been credited with saving hundreds of lives.

"The extent of destruction is unimaginable," Reuters cameraman Rafiqur Rahman reported by telephone from a coastal village.

"In the 7 km (4.5 miles) I trekked this morning, I saw not a single house standing," he said. "Only a few leafless trees and a couple of dogs reminded me it was once a village," he said.

UNICEF said cyclone Sidr had affected 3.2 million people and put 1 million in shelters.

"The people here (in Bangladesh) are highly resilient but it has been a hard year for them," Louis-Georges Arsenault, UNICEF Representative in Bangladesh, said.

"... many children are finding themselves in difficult circumstances without food, shelter and safety - they have suffered loss or separation from their parents (following the cyclone)," Arsenault said in a statement.

"I urge the international community to keep Bangladesh high on its priority (list) as the rehabilitation following the devastating cyclone is going to need as much support as possible,"

1,000 MISSING FISHERMEN

World Vision, one of many NGOs working to help the cyclone survivors, said on Monday some 1,000 fishermen were still unaccounted for in the Bay of Bengal.

"All at once, our house was taken away like a toy. We discovered ours on the ground but without its roof and walls," said Rika Halder, a girl of Kandi village in southern Mongla.

The house was made of corrugated iron, she told Rafael Palma of World Vision. "I need to put a roof over the head of my children. But I don't know how I am going to do this," said Nirmal Moitra, 45, another Mongla resident.

"We have seen more bodies floating in the sea," the Daily Independent newspaper quoted fisherman Zakir Hossain as saying. Zakir returned from the Bay alive but brought along two decomposed bodies, the daily said.

"It is apprehended that hundreds, even thousands, might have been swept into the sea and got a watery burial," it added.

Pope Benedict called on Sunday for international aid. Bangladesh appealed to the International Red Cross for $6 million, while the European Union and the United States have pledged millions more.

Two U.S. Navy amphibious assault ships with helicopters, the USS Essex and the USS Kearsarge, were sailing to Bangladesh to help in relief and rescue operations, a U.S. embassy statement said on Sunday.

Helicopters flew sorties to devastated areas, dropping food, drinking water and medicine for the survivors.

"But there are not many places where we can land," said one pilot, as large areas were still under water.

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