A 40-year old four-storey building collapsed in the Indian city of Mumbai on Tuesday, killing at least eight people with more than 20 feared trapped, fire and police officials said.

"Search and rescue operations are still on," said P.S. Rahangdale, chief fire officer of the Mumbai Fire Brigade, adding two firemen were injured during the rescue operation. A total of 16 people had been rescued so far, he said.

The ground floor of the building in the suburb of Ghatkopar housed a nursing home, which was vacant at the time, while the rest of the building was occupied by three or four families on each floor, he said.

Building collapses are common in India, especially during the annual monsoon season which usually runs from late June to September.

Millions of Indians are forced to live in cramped, ramshackle properties because of rising real estate prices and a lack of housing for the poor.

High demand and lax regulations have encouraged some builders to cut corners, use substandard materials or add unauthorized extra floors.

In the eastern city of Kolkata, a portion of an almost century-old building collapsed killing two people and some were feared trapped, media channels reported.

In 2013, 145 people were killed in three separate building collapses around Mumbai, on the western coast, the highest in recent years.

A building being constructed illegally in Mumbai caved in that year, killing 74 people in the country's worst building collapse in decades.

A dilapidated building killed 12 people when it collapsed outside Mumbai in August 2015.

Nine people died the same month when another old three-storey building collapsed in monsoon rain in the Mumbai suburb of Thakurli.

At least four people were killed in two incidents in April and August last year when buildings collapsed in the city.