At least 22 people were killed, 16 of them in India's financial capital Mumbai, and over 80 injured in separate incidents of wall collapse in Maharashtra today following heavy rains.

Authorities declared a public holiday in Mumbai city which has come to virtual standstill due to water-logging on roads and rail tracks, reports our New Delhi correspondent.

Thirteen people were killed as a compound wall came crashing down in Mumbai's Malad East early this morning. In Thane's Kalyan, near Mumbai, three persons, including a three-year-old boy, died when the wall of a school crashed on two houses.

In Pune, six labourers were killed and at least two injured when a wall collapsed on their makeshift shelters in Ambegaon locality, officials said.

"As per information, the wall collapsed on the makeshift shelters of labourers in which six people died and two-three others were injured," an official said.

Heavy rain lashed Mumbai and its surrounding areas overnight, flooding the airport and paralyzing movement of local trains, the lifeline of Mumbai which experienced the heaviest rain over a 24-hour period in a decade.

The Indian met department has sounded a red alert for Mumbai today, warning for heavey to extremely heavy rains.

The Indian Navy has deployed several teams to assist the Mumbai civic body to help people stranded in flooded areas.

Several suburban and long-distance trains have been cancelled as railway tracks were flooded and more than 52 flights cancelled and 54 diverted because a SpiceJet plane that skidded last night while landing in rain has forced a shutdown of the main runway at the Mumbai airport.

Maharashtra government declared a public holiday in Mumbai and Thane, with Chief Minister Devendra Fadnavis urging people to stay indoors unless absolutely necessary.

The state government said that barring emergency services, all government offices will remain closed in Mumbai today. While all schools and colleges are closed today, private firms have asked employees to work from home.