Diesel-guzzling trucks and commercial vehicles in India will soon have to pay a surcharge for entering New Delhi, after the country's top court Friday approved a trial plan to improve the capital's notoriously filthy air.

Successive Delhi governments have been criticised for failing to curb pollution from industry and chronic traffic in the city of 17 million, ranked as having the world's worst air quality by the World Health Organisation.

Acting on a petitioner's plea, the Supreme Court approved an extra charge of 700 rupees ($11) on light commercial vehicles and 1,300 rupees on large trucks entering Delhi.

The court is scheduled to pass an official order Monday on the surcharge, which it said would apply for four months on an "experimental basis", with no start date yet specified.

Oil tankers, passenger buses, ambulances and trucks carrying some foodstuffs will not have to pay up, the court added.

Many environmental activists welcomed the toll, saying it would help to clear the capital's polluted air before winter starts, when quality deteriorates.

But campaign group Greenpeace India called the move a "temporary solution" that focused on diverting pollution rather than reducing it.

"Even if the trucks don't enter the capital, they are still polluting other parts of the country," campaigner Nandikesh Sivalingam said in a statement to AFP.

"Air pollution is no longer a Delhi issue, it's a national issue."

Banned from the city during the day, thousands of trucks pour into Delhi every night adding to the toxic cocktail of smog, according to the Delhi-based Centre for Science and Environment (CSE).

The independent centre says about 52,000 commercial vehicles enter the city daily -- more than double government estimates -- accounting for nearly a third of the area's total pollution levels.

Many of the trucks drive through the capital to avoid paying tolls outside the city.

- Premature deaths -

Friday's decision comes a month before Diwali, the Hindu festival of light, when Delhi fills with acrid smoke from celebratory firecrackers set off day and night, blanketing the city in an eye-burning haze.

A WHO study of 1,600 cities released last year showed Delhi had the world's highest annual average concentration of small airborne particles known as PM 2.5 -- higher even than Beijing.

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

Delhi is expected to have the world's highest number of premature deaths due to air pollution by 2025 with nearly 32,000 fatalities, a study by Germany's Max Planck Institute for Chemistry showed.

India's environment court earlier this year ordered a ban on diesel vehicles older than 10 years in Delhi, but the embargo has not yet been introduced.

Delhi authorities have been mulling a plan to prohibit the use of cars on certain busy stretches of road once a month, while also encouraging car pooling and greater use of public transportation.