After weeks of heavy rains a dam collapsed in the northeastern Brazilian state of Bahia, swamping already swollen local rivers and threatening to trigger flash floods, regional authorities said late on Saturday.

The Igua dam is near the city of Vitoria da Conquista in southern Bahia, leading authorities to evacuate residents at risk downriver, mainly in the town of Itambe.

There were no reports of deaths or injuries or major damage, though details of the incident remained limited.

"A dam with a large volume of water has collapsed and a strong flash flood will impact the municipality of Itambe," the Itambe town hall posted on its official Instagram account.

"All residents should evacuate the margins of the Verruga river urgently," it added.

Itambe is an agricultural region in southern Bahia located about 200 kilometers (125 miles) inland from the coastal city of Ilheus.

The mayor of Vitoria da Consquista, Sheila Lemos, said all residents close to the river had been evacuated.

In a posting on the city's website, Lemos said the flooding threatened to cut off the BR-116 highway, a major truck route between northeastern and southern Brazil.

Bahia Governor Rui Castro said at least 300 people have been evacuated from each of some 20 towns in the state that were hit by floods caused by heavy rainfall for almost two months.

"Thousands of people have had to leave their homes because the water rose one or two meters, even three meters in some places," he told reporters on Saturday.

The rains have caused 17 deaths in Bahia since the beginning of November, and 66 towns are facing emergency situations, civil defense officials said.

In the state capital of Salvador, weather officials said December rainfall has been six times greater than the average.