Rescuers were seen using hands to dig up the ground to retrieve bodies, local television showed, and authorities said more could be trapped inside the debris.

Four of those injured were taken to a nearby hospital, officials said. Local television news channels showed rescuers carrying the injured on makeshift stretchers using cloths inside narrow lanes.

In one of the neighbourhoods, about half a dozen huts located at the base of a hillock, collapsed on top of each other, officials said.

Several areas in the city were waterlogged after heavy rainfall over the last 24 hours and suburban train services were disrupted, crippling India's financial capital, where incidents of building collapses have become more common during the monsoon.