Death toll from Brazil floods rises as officials warn 'much worse' is ahead

The death toll from floods and mudslides triggered by torrential storms in southern Brazil has climbed to 39, officials said, as they warned of worse to come.

Rising water levels in the state of Rio Grande do Sul was putting strain on dams and threatening the metropolis of Porto Alegre with "unprecedented" flooding, authorities warned on Friday.

"Forget everything you've seen; it's going to be much worse in the metropolitan region," Governor Eduardo Leite said on Friday as streets of the state capital, with a population of some 1.5 million, started flooding after days of heavy downpours in the region.

The state's civil defence department said at least 265 municipalities have suffered storm damage in Rio Grande do Sul since Monday, injuring 74 people and displacing more than 24,000 — a third of whom have been brought to shelters.

At least 68 people were missing, and more than 350,000 have experienced some form of damage, according to the latest data.

And there was no end in sight, with officials reporting an "emergency situation, presenting a risk of collapse" at four dams in the state.

Rio Grande do Sul's 'worst disaster'

The level of the state's main Guiaba river, meanwhile, was estimated to have risen 4.2-4.6 metres, but could not be measured as the gages have washed away, the mayor of Porto Alegre said.

As it kept rising, officials raced to reinforce flood protection.

Porto Alegre's worst recorded flood was in 1941 when the river reached a level of 4.71 metres.

Elsewhere in the state, several cities and towns have been completely cut off from the world in what Governor Leite described as "the worst disaster in the history" of Rio Grande do Sul.

Many communities have been left without access to drinking water, telephone or internet services. Tens of thousands had no electricity.

President Luiz Inacio Lula da Silva visited the region on Thursday, vowing "there will be no lack of human or material resources" in responding to the disaster, which he blamed on the climate crisis.

Back in Brasilia, Lula again vowed on Friday that his government would support local rescue and reconstruction efforts.

The central government has sent aircraft, boats and more than 600 soldiers to help clear roads, distribute food, water and mattresses, and set up shelters.

School classes have been suspended state-wide.

'Disastrous cocktail'

Climatologist Francisco Eliseu Aquino told the AFP news agency on Friday the devastating storms were the result of a "disastrous cocktail" of the El Nino weather phenomenon and global heating combined.

South America's largest country has recently experienced a string of extreme weather events, including a cyclone in September that claimed at least 31 lives.

Aquino said the region's particular geography meant it was often confronted by the effects of tropical and polar air masses colliding — but these events have "intensified due to climate change."

And when they coincide with El Nino, a periodic weather system that warms the tropical Pacific, the atmosphere becomes more unstable "and conducive to storms in the Rio Grande do Sul," he said.

Extreme flood hit the state in the last two years at "a level of recurrence not seen in 10,000 years," said Aquino, who heads the Federal University of Rio Grande do Sul's geography department.

Brazil's north recently experienced a historic drought, and the number of forest fires reached a record in the first four months of this year.

"Rain in the south, fire in the north... These two tragedies bear the fingerprints of the climate crisis," the Climate Observatory NGO warned in a statement.