Much of Bahia, home to about 15 million people, has suffered from intermittent flooding for weeks, after a long drought gave way to record rains. Flooding in some areas intensified late on Christmas Eve and early on Christmas Day after a pair of dams gave way , sending residents scrambling for higher ground.

Rescue workers on Monday patrolled in small dinghies around the city of Itabuna, in southern Bahia, plucking residents from their homes, including some who escaped through second-floor windows.

Bahia Governor Rui Costa said on Twitter that 72 municipalities were in a state of emergency.

"Unfortunately, we're living through the worst disaster that has ever occurred in the history of Bahia," he wrote.

Manfredo Santana, a lieutenant-colonel in Bahia's firefighting corps, told Reuters that emergency workers had rescued 200 people in just three nearby towns. The heavy currents of the swollen Cachoeira River complicated rescue efforts.

"It's difficult to manoeuvre even with jet skis," he said. "Rescue teams had to retreat in certain moments."

Bahia's civil defence agency said 20 people had died in 11 separate municipalities.

Newspaper O Globo, citing a state firefighting official, said that authorities are monitoring an additional 10 dams for any signs they may collapse.

The scrutiny of public infrastructure and urban planning comes two years after the collapse of a mining dam in neighbouring Minas Gerais state killed about 270 people

In televised remarks, Costa, the Bahia governor, attributed the chaotic scenes in part to "errors that have been committed over the course of years".

Australian Associated Press