Brazilians yesterday prayed for victims of devastating floods near Rio de Janeiro after the death toll from the natural disaster rose to at least 610 and was predicted to climb again.

Emergency workers in the disaster zone, in the Serrana region just north of Rio, were overwhelmed by the body count. Refrigerator trucks had to be brought in to store corpses.

Workers transporting bodies said they feared the overall death toll could top 1,000 as rescuers reached outlying hamlets.

President Dilma Rousseff declared the three days of mourning, government news agency Agencia Brasil reported. Rio de Janeiro state authorities said their state will observe a full week of mourning starting today.

As of late on Saturday, the death toll stood at 610 people, with the worst-hit towns being Teresopolis, Nova Friburgo and Petropolis, civil defence officials said. Outlying villages also reported deaths.

An estimated 14,000 people were assisted by rescue workers or lost their homes in the Serrana area towns hardest hit about 100 kilometres from coastal Rio, civil defence figures showed.

The single hardest hit town was Nova Friburgo, where 274 people were killed. Nearby Teresopolis had 263 dead, 55 were killed in Petropolis and 18 lost their lives in Sumidouro, officials said.

“I think in the end we’ll see more than 1,000 bodies,” said a funeral worker in Teresopolis, Mauricio Berlim. “In one village near here, Campo Grande, there were 2,500 homes and not one is left standing.”

Authorities also made an urgent appeal for donations of blood, bottled water, food and medicine.

At least four refrigerated trucks were parked out the front of an overflowing makeshift morgue inside a Teresopolis church.

At the town’s cemetery, a dog curled up at the grave site of his mistress, a woman named Cristina Maria de Santana, refusing to leave even though she had been buried two days earlier, workers said.

Body recovery efforts have been hampered by tons of mud that, in some cases, have cut villages off and made them accessible only by helicopter – but flights were limited by persistent rain that hindered visibility in the rough terrain to just a couple hundred metres.

At least a dozen remote hamlets remained out of touch, and one witness reported seeing a group of people buried in their car by a river of reddish mud.

The disaster, which media called the worst tragedy of its kind in Brazil’s history, struck sleeping families on Wednesday before dawn.

Seasonally heavy rains were suddenly intensified by a cold front, dumping a month’s worth of precipitation in just eight hours.

Water, food and electricity were lacking in some areas of the Serrana, with authorities struggling to deliver supplies over fully or partially collapsed roads. Telephone communications were unreliable though progressively being restored.

A municipal official in Teresopolis, Solange Sirico, told Brazilian television there was a risk of epidemics breaking out as bodies decomposing in the tropical heat mingled with water runoff.

Ms Sirico said the 1,200 doctors working in the town were overwhelmed, and medical supplies were needed.