The death toll in catastrophic floods which left thousands homeless in the Malian capital Bamako rose to 34 on Friday, one of the leaders of the rescue operation said.

More than 100 homes, mostly poorly constructed mud-brick buildings on drainage sites, were swept away as the Niger river burst its banks in torrential rain on Wednesday, bringing down bridges and submerging entire streets.

"I have been told of 34 dead. Damage to property is widespread and the evaluation is ongoing," said Die Dao, deputy head of the Department of Civil Protection rescue mission.

On Thursday, a government official had put the death toll at 23 people.

Flooding often leads to widespread displacements and casualties during west Africa's June to October rainy season, as well as disease outbreaks due partly to poor sanitation.

Local television broadcast images of homeless residents wandering Bamako's streets, apparently in shock, as others waded through chest-high, fast-flowing muddy water to rescue stranded neighbours.

The old hillside district of Taliko suffered the brunt of the flooding, with victims finding refuge in a primary school equipped with mats, kettles and mosquito nets.

Headmaster Abdoul Konate said the victims were desperate for money and clothes.

"They said that they have lost all their savings. There are 80 of them, about half of whom are children," he told AFP.

Elsewhere in Bamako residents told of their horror as water levels began to rise at great speed, with many blaming local government for not maintaining the city's drains and not providing enough disaster relief in the immediate aftermath.

"I have a family of six people. My mud brick house collapsed in the rain. We have nothing to eat so we need food and also the means to rebuild our house," Boubacar Coulibaly, 52, told AFP.

"Up to now we have received nothing in terms of support."

"I have lost my papers. I have recovered some clothes that my wife is in the process of washing," said Samba Guindo, 51, a driver and father of six.

His wife, Saran Camara, said she had hoped long before Wednesday's floods to move away from her dangerous housing area, situated in a swamp.

"If I don't leave, my children will die and that keeps me up at night," she said.

Satigui Camara, 25, said he could only stand by and watch as his family home collapsed.

"I support my mother because my father is no longer alive. But I've got no way of making a living, no work," he said as he sat on the trunk of a tree, imploring the authorities to help him.

Although a major gold producer, impoverished Mali has been deserted by tourists and foreign investors and economic growth is at a 10-year low as the country struggles to emerge from months of conflict.

Last year Mali was upended by a separatist rebellion and coup that toppled the elected president and allowed Al-Qaeda-linked Islamist fighters to occupy the north before being ousted by a French-led military intervention.

The flooding in Bamako is the first big challenge to face president-elect Ibrahim Boubacar Keita since his election on August 11, which was also marred by heavy rain in the capital and flooding in the north.