The bad weather affected 77 municipalities across the state, with almost 100 people forced to evacuate their homes and another 200 taken to shelters, officials said in a statement.

President Luiz Inacio Lula da Silva posted on social media that he spoke with state governor Eduardo Leite and offered assistance.

"The federal government will join the efforts of state government and municipalities to get through this difficult time, which is the result of climate change affecting the planet," the president wrote on X.

With weather conditions deteriorating, authorities were scrambling to rescue people cut off by floodwaters.

"In the coming hours, the volume of rainfall is expected to remain elevated... All monitored rivers are at levels above their alert limits," Rio Grande do Sul's government said in a statement.

Torrential rains in late March in southeastern Brazil left at least 25 people dead in the states of Rio de Janeiro and Espirito Santo.

Brazil's south and southeast have been battered by a cold front that followed a wave of extreme heat.