Hundreds of taxi drivers protested in New Delhi on Monday against a ban on diesel cabs, the latest initiative aimed at improving air quality in the world's most polluted capital.

India's top court on Saturday ordered taxis run on the dirty fuel off the city's roads, refusing industry requests for more time to switch to greener compressed natural gas (CNG).

Many of Delhi's taxis already run on CNG, but the ban will impact about 30,000 traditional cabs and some working for app-based Uber and Ola services, according to taxi operators.

The Supreme Court has been pressuring authorities to reduce dangerous levels of haze and dust that choke the city, with a string of orders last year including a ban on new, large diesel cars, affecting all road users.

Angry taxi drivers blocked key intersections in Delhi and neighbouring satellite city of Gurgaon on Monday morning, bringing peak-hour traffic to a standstill for hours.

"You can't have knee-jerk solutions to long-standing problems," Balwant Singh, who heads a taxi union of 500 members, told AFP at a noisy demonstration in central Delhi.

"Why go after commercial passenger vehicles only? Private diesel cars are running freely on the roads, why not stop them?"

Some drivers said they knew of no available technology to switch from diesel to CNG and would instead be forced to buy new taxis.

"I sold my house to buy the taxi and now I will have to sit at home and twiddle my thumbs. How will my family of five survive you tell me," said driver Tarun Kumar.

A 2014 World Health Organisation survey of more than 1,600 cities ranked Delhi as the most polluted, partly because of the nearly 10 million vehicles on its roads.

The ban by the court, which was acting on a petition, came just days after the end of another two weeks of "odd-even" that kept about one million cars off Delhi's roads.

The government scheme, first tested in January, restricts cars to alternate days according to whether they carry odd or even-numbered licence plates.

But Delhi-based research institute TERI said its analysis found the measures had not significantly reduced concentrations of PM 10 and PM 2.5 during the first week.

These fine particles measuring less than 2.5 micrometres are linked to higher rates of chronic bronchitis, lung cancer and heart disease.