At least 10 people have died after Kolkata city in the eastern Indian state of West Bengal saw its heaviest rainfall in 39 years.

Nine of the deaths were caused by electrocution in stagnant water.

Residential areas and businesses in the city and its suburbs have been grappling with severe waterlogging since Monday night. Several key roads remain flooded and train services are disrupted, forcing commuters to wade through knee-deep waters.

The flooding comes days before Durga Puja, the region’s biggest and most popular annual festival when tens of thousands come out to worship the Hindu goddess Durga.

The deluge – reported to have brought down 251.4mm in less than 24 hours – is the worst the city has seen since 1986. It was also the region’s sixth-highest single-day of rainfall in the past 137 years.

India’s weather department said the rains were a result of a low-pressure area, which developed over the north-east Bay of Bengal.

The city is on alert with more rains predicted for the next few days.

West Bengal Chief Minister Mamata Banerjee said she had “never seen such rain” and lamented the loss of life, promising compensation to the victims’ families.

As many of the deaths were from electrocution, authorities switched off power in many places to prevent further accidents.

Efforts to restore normalcy were under way, officials said on Tuesday night.