Death toll from devastating mudslides and floods that swept through a mountainous region of Rio de Janeiro state reaches 78, local authorities say.

Firefighters and volunteer rescue workers dig through remains of houses washed away in torrents of mud, many of them in impoverished hillside slums.
Firefighters and volunteer rescue workers dig through remains of houses washed away in torrents of mud, many of them in impoverished hillside slums. (AP)

At least 78 people have been killed in devastating flash floods and landslides that hit the picturesque Brazilian city of Petropolis, turning streets into torrential rivers and sweeping away houses, Governor Claudio Castro has said.

Rescue workers on Wednesday raced to find survivors buried in the mud and wreckage after heavy storms a day earlier dumped a month's worth of rain in three hours on the scenic tourist town in the hills north of Rio de Janeiro.

There were fears the death toll could rise further as firefighters and volunteer rescue workers dug through the remains of houses washed away in torrents of mud, many of them in impoverished hillside slums.

At least 21 people have been so far been rescued alive in the effort, according to the state government.

Around 300 people were being housed in shelters, mostly in schools, officials said. Charities called for donations of mattresses, blankets, food, water, clothing and face masks for victims.

READ MORE: Hundreds left homeless from deadly landslides, floods in Brazil's Sao Paulo

'War zone'

Wendel Pio Lourenco, a 24-year-old resident, was walking through the street with a television in his arms, heading to a local church in search of shelter.

He said he was trying to save a few possessions, after spending a sleepless night helping search for victims.

"I found a girl who was buried alive," he said. "Everyone is saying it looks like a war zone."

Governor Claudio Castro said much the same after visiting the scene. "It's almost a war situation. We've mobilised our entire team," he said.

READ MORE: Deaths as heavy rains torment southeastern Brazil

"It's devastating. We never could have imagined something like this," says one fleeing resident, Elisabe th Lourenco. (AP)

Three days of mourning

Videos posted on social media from Tuesday's rains showed streets in Petropolis, the 19th-century summer capital of the Brazilian empire, filled with gushing floods that swept away cars, trees and nearly everything else in their paths.

Many shops were completely inundated by the rising waters, which gushed down the streets of the historic city center.

Officials said more than 180 firefighters and other rescue workers were responding to the emergency, aided by 400 soldiers sent in as reinforcements.

City hall declared a "state of disaster" in the city of 300,000 people, which sits 68 kilometres north of Rio.

The city council declared three days of mourning for victims.

Source: AFP