India, Sept. 24 -- An overnight spell of torrential rainfall, the heaviest in nearly four decades, inundated Kolkata and its outskirts on Tuesday morning and killed 11 people, leaving the 335-year-old metropolis struggling to stay afloat and seriously jeopardising preparations for the Durga Puja festival.

Officials from the India Meteorological Department (IMD) said that the rainfall - 98mm per hour - was just shy of the threshold for a cloudburst (100mm an hour). But the six-hour spell marooned a vast swathe of the city of 15 million people, cut off entire neighbourhoods, paralysed rail, road and air services, drowned vehicles and poured columns of gushing water into people's homes and apartments.

"I was supposed to take my mother to a...