A roof has collapsed at a departure terminal at the main airport in India's capital, New Delhi, killing one person and causing authorities to cancel flights from one terminal, officials and media have said.

A portion of the canopy at the departures area of Delhi Airport's Terminal 1 collapsed at 5am on Friday, a statement from the airport posted on the social media site X said.

"There are injuries reported and emergency personnel are working to provide all necessary assistance and medical aid to those affected," the statement said.

Eight injured people were taken to hospital and the rescue operation had been completed, said Atul Garg, the director of Delhi Fire Service.

At least 10 flights were cancelled and 40 were delayed, according to data from flight tracking platform Flightradar24.

All departures from the terminal of low-cost carriers IndiGo and SpiceJet were cancelled until 2pm, the statement said.

Visuals from media showed water pouring from the collapsed roof and a taxi stuck under a pillar, even as rain continued to pelt down in the area, leading to inundated roads and traffic jams.

India's aviation minister said he was monitoring the situation and that first responders were working at the site.

Many other parts of Delhi were flooded as well and cars trapped in thigh-deep water. Metro services were affected and traffic snarls were reported from several parts of the city.

Several residents in Delhi also complained of power cuts.

In India's most populous state of Uttar Pradesh, at least 20 people died in various rain and flood-related incidents in the last 48 hours, including seven due to lightning strikes, officials said.

The entire terminal, one of three at the country's busiest airport, has been evacuated and an inquiry ordered into the collapse, said the minister, Kinjarapu Rammohan Naidu.

Reuters