MUMBAI – A wall collapsed and killed at least 22 people in Mumbai on Tuesday as the heaviest monsoon rains in a decade brought chaos to India's financial capital and surrounding areas.

Scores more were injured when the structure came down at nighttime in a slum, said Tanaji Kamble, a disaster management spokesman for Mumbai's local authority.

By late Tuesday one more person had succumbed to injuries, increasing the previous death toll of 21, the Press Trust of India reported.

The tragedy came during heavy rains which lashed the teeming coastal city of 20 million residents for a second consecutive day, bringing it to a virtual standstill.

Authorities declared on Tuesday a public holiday and advised all residents to stay indoors. Schools and colleges were closed while more than 100 flights were either cancelled or diverted from Mumbai airport.

The airport's main runway was shut after a SpiceJet plane carrying 167 passengers and crew overshot it shortly before midnight Monday.

"Currently secondary runway is in use, our team is trying their best to bring the main runway back in operation and this may take up to 48 hrs," the airport tweeted.

According to Skymet Weather, a private weather-tracking agency, large swathes of Mumbai received around 350 millimetres (13 inches) of rain overnight into Tuesday morning, the most in a decade.

The deluge left low-lying areas submerged. 

"Everything around us is flooded. It's scary and the problem persists the Dharavi slum, said.

Around 1,000 people living close to the city's Mithi river were evacuated to higher ground as it threatened to burst its banks, said Kamble, the disaster management spokesman.

Waterlogged tracks disrupted train services on Mumbai's colonial-era rail network, a lifeline for the city's population, while motorists were seen pushing cars through flooded streets.

Rescuers sifted through the debris of the collapsed wall in Mumbai's north, hoping to find more survivors. – AFP