Indian tech hub Bangalore has been inundated by floodwater after torrential downpours that have killed scores of people across the country's south in the past few weeks.

A man wades through a waterlogged area in Bangalore
A man wades through a waterlogged area in Bangalore AFP / Manjunath Kiran

Lakes dotted around the city have overflowed after three days of ferocious rain, submerging roads and flooding homes.

Rescuers deployed inflatable life rafts to retrieve stranded residents while buses and motorised rickshaws carted commuters through knee-deep water.

Many roads have been left submerged by the flooding in Bangalore
Many roads have been left submerged by the flooding in Bangalore AFP / Manjunath Kiran

"We can't go inside our house because the water has stagnated in front of it," Bangalore resident Rathnamma told AFP on Monday.

"All our groceries are inside and we have been stuck outside the house since 10 o'clock last night," she added.

Residents outside a flooded apartment block in Bangalore
Residents outside a flooded apartment block in Bangalore AFP / Manjunath Kiran

Experts say unpredictable and extreme weather across South Asia is being driven by climate change, exacerbated by damming, deforestation and excessive development.

At least 30 people have been killed after flash floods around southern India in recent days, according to local media reports.

Another 42 died last month when heavy rains pummelled the coastal state of Kerala, prompting authorities to suspend an annual pilgrimage to Sabarimala, site of one of Hinduism's holiest shrines.

A week of pounding rains also hit the city of Chennai earlier in November, flooding most main roads and uprooting trees.