Video | Brazil floods claim more than 500 deaths so far

Officials in the Serrana region just north of Rio said at least 506 people were killed, surpassing the 437 killed in a 1967 mudslide tragedy that had been previously considered Brazil's biggest disaster.

More bodies were expected to turn up as rescuers finally reached villages cut off because of destroyed roads and bridges in the region.

Frantic efforts to locate survivors and bodies braved the risk of further mudslides, as rain continued to fall on the waterlogged region, making it even more unstable.

"It's very overwhelming. The scenes are very shocking," President Dilma Rousseff said after visiting the area yesterday.

She pledged "strong action" by her government, which has already released 470 million dollars in initial emergency aid and sent seven tonnes of medical supplies.

The catastrophe was seen as her first big test since taking power two weeks ago, replacing her popular predecessor, Luiz Inacio Lula da Silva.

Storms early Wednesday dumped the equivalent of a month's rain in just a few hours before dawn, sending mudslides slicing through towns and hamlets, destroying homes, roads and bridges and knocking out telephone and power lines.

The worst affected towns were Novo Friburgo, which recorded 225 deaths, Teresopolis, with 223 deaths, and Petropolis, with 39 deaths, according to municipal officials. Another 19 fatalities were registered in the village of Sumidouro.

The toll of dead from this one disaster was higher than the 473 rain-related deaths recorded for all of Brazil over the span of 2010.

Churches and police stations were turned into makeshift morgues, the smell of decomposing corpses heavy in the warm air. Thousands of survivors took refuge in shelters.

The atmosphere was mournful as the extent of the disaster became apparent in Teresopolis, a mountain town devastated by the mudslides.

Bodies piled up in makeshift morgues while, crowds of people desperate to learn the fate of loved ones gathered outside.