Wall collapses caused by heavy monsoon rains in India have killed 27 people, as bad weather continued to disrupt road, rail and air traffic in Mumbai for the second day.

Heavy rain brought a wall crashing down on shanties built on a hill slope in Malad, a western suburb of Mumbai, a fire brigade official said. At least 18 people were killed in the incident.

In a separate incident, three people died when a school wall collapsed in the city of Kalyan, 42km north of Mumbai.

In the nearby western city of Pune, six people were killed in a wall collapse on Tuesday, a fire brigade official said, after a similar incident on Saturday killed 15.

More than 300mm of rain fell over 24 hours in some areas of Mumbai, flooding streets and railway tracks, forcing the suspension of some suburban train services, which millions of commuters ride to work each day.

As intermittent heavy showers and isolated extremely heavy rainfalls are forecast, authorities declared a holiday for government offices and educational institutions.