Rescue workers are struggling to reach areas cut off by devastating floods and landslides that have killed at least 375 people in one of Brazil's worst natural disasters in decades.

Torrents of mud and water set off by heavy rains have left a trail of destruction through the mountainous Serrana region near the city of Rio de Janeiro, toppling houses, buckling roads and burying entire families.

‘It's like an earthquake struck some areas,’ said Jorge Mario, the mayor of the Teresopolis municipal area, where at least 158 people have died.

‘There are three or four neighbourhoods that were totally destroyed in rural areas. There are hardly any houses standing there and all the roads and bridges are destroyed.’

Heavy rains earlier in the week killed 13 people in Sao Paulo state, bringing the total number of deaths in southern Brazil to at least 388.

The disaster poses an early challenge for new President Dilma Rousseff, who was due to fly over the region today.

Beside the immediate crisis of loss of life and property damage, it could further boost rising food prices that have been a major concern for the government.

Hillsides and riverbanks about 100km north of Rio, which will co-host the 2014 World Cup and host the 2016 Olympics, collapsed after the equivalent of a month's rain fell in 24 hours from Tuesday.

Folha de Sao Paulo newspaper said it was the worst natural disaster to hit Brazil in four decades.

More heavy rain is forecast for the coming days, complicating rescue efforts and raising the risk of further mudslides.

Raging flood waters and rivers of mud totally submerged some houses and left cars crumpled like tin cans. More then 13,500 people have been made homeless in the region, the Civil Defence agency said.

The worst-hit area is Nova Friburgo, a rural town first settled by Swiss immigrants, where the death toll was 168, according to local officials.

Mario said rescue teams had yet to reach several of the worst-hit parts of Teresopolis, including one neighbourhood where media reports said that around 150 houses were destroyed.

Dozens of bodies have been lined up outside a police station in the city centre awaiting identification before being moved to a church, local taxi driver Vinicius Bittencourt told Reuters.

‘The bodies were there because there is no more space in the morgue,’ he said. ‘People are walking in the street crying. I've seen people carrying dead children wrapped in blankets.’

At least 36 people also died in Petropolis, a picturesque town nestled in the mountains that served as the summer residence for Brazil's royal family in the 19th century.

Another 13 people died in the town Sumidouro in the same region, officials said.

Many stranded residents were forced to fend for themselves as rescue operations were hampered by destroyed roads and treacherous terrain.

Television images showed one woman holding a dog in the ruins of her house as powerful floodwaters tore at the remaining walls.

She grabbed a rope thrown by residents from a nearby rooftop and was eventually pulled to safety, after dropping the dog into the vicious current.

Rescuers dug desperately in the ruins of houses in search of survivors, often finding only corpses. One success came when a six-month-old baby was rescued alive from the rubble of a house, drawing cheers from residents.