India's prime minister suggested Monday the country's "age-old traditions" could be used to ease its choking smog, as he launched a new air quality index for the world's most polluted capital.

Narendra Modi proposed making every Sunday "bicycle day" and switching off street lights during a full moon, amid growing public concern over the impact of air pollution on the health of India's 1.2 billion people.

"There can be green solutions in our age-old traditions," he said in a speech at a conference of environmental policymakers in the capital New Delhi.

"What if our city governments... decided not to switch on the street lights during a full moon?" he said.

"It is only a small thing, but you can imagine how much energy could be saved and emissions could be cut if all the street lights were switched off during a full moon."

The government said the new index would initially cover 10 cities -- Delhi, Agra, Kanpur, Lucknow, Varanasi, Faridabad, Ahmedabad, Chennai, Bangalore and Hyderabad -- each of which would have monitoring stations with Air Quality Index display boards.

The government is under intense pressure to act after the World Health Organization last year declared New Delhi the world's most polluted capital.

At least 3,000 people die prematurely every year in the city because of air pollution, according to a joint study by Boston-based Health Effects Institute and Delhi's Energy Resources Institute.

Modi also signalled that India would not bow to foreign pressure on tackling climate change, ahead of UN-led talks late this year in Paris on reducing greenhouse gas emissions.

"The world guides us on climate change and we follow them? The world sets the parameters and we follow them? It is not like that... India can lead the world," he said.

Environment Minister Prakash Javadekar said the new index could drive efforts to ease air pollution.

But he gave little indication of what the government would do except to promise new rules on disposing of construction waste.

The dust from India's thousands of industrial and construction sites adds to the fumes from millions of vehicles to create the toxic cocktail that city-dwellers breathe.

Many experts were unimpressed.

"Monitoring pollution is not a solution to stop pollution," said ecologist Vandana Shiva, adding Modi's campaign to attract foreign companies to manufacture in India would only exacerbate the problem.

"It's like finding a very sick person and instead of treating him, you hand him a thermometer. You have to take strict policy action, not launch symbolic measures."

Greenpeace welcomed the new index but said it had expected the government "to address the issue with more rigour and responsibility".

"Delhi is facing a public health emergency and an air quality index needs to be matched with actionable plans on how to bring the pollution levels down," said campaigner Aishwarya Madineni in a statement.

"This is merely (a) bandaid on a wound that needs stitches, the bleeding is going to continue."

- Delhi worse than Beijing -

A World Health Organization study of 1,600 cities released last year showed Delhi had the world's highest annual average concentration of small airborne particles known as PM2.5 -- higher even than Beijing.

These extremely fine particles of less than 2.5 micrometres in diameter are linked with increased rates of chronic bronchitis, lung cancer and heart disease as they penetrate deep into the lungs and can pass into the bloodstream.

India disputed the WHO's assertion, but has conceded that air pollution in the capital is comparable with that of Beijing.

An air quality index compiled by the US embassy in Delhi on Monday registered a PM2.5 reading of 175, which is considered unhealthy.

The reading from the US embassy in Beijing was just 53, which is considered moderate.

A new government website for the index, which will provide colour-coded air quality rankings ranging from "good" to "severe", went live on Monday morning, but could not be accessed. Officials said it had likely collapsed under high demand.

The aim is for the index to eventually cover 66 cities.

The government gave few details about the new rules on construction waste. Delhi generates up to 4,000 tonnes of construction debris every day, according to a 2014 study by the Centre for Science and Environment.

Policymakers have suggested restrictions on private vehicles, higher pollution-related taxes and stricter enforcement of urban planning laws.