Delhi's smog crisis headed for a new toxic peak on Saturday but farmers are refusing to stop the stubble burning that is widely blamed for the poisonous clouds engulfing the Indian capital.

Air pollution in parts of the city reached "severe" levels Saturday - a day after US President Donald Trump described Indian air as "filthy" - with monitoring agencies warning it would worsen in the next two days because of the lack of wind.

Teams in states around Delhi, home to some 20 million people, are hunting the illegal stubble burners, even driving around country roads at night when most fires are started.

In the past month some 1,265 farmers have been fined in Punjab alone, according to senior pollution officer Krunesh Garg, but satellite detectors have recorded more than 12,000 fires in the state.

In a bid to step up the campaign, the government is offering subsidised machines to clear rice paddies and farmers who are caught starting fires are blocked for bank loans.

But thick grey clouds of smoke that carry deadly particles to the world's most polluted capital can still be seen everywhere.

Because of Delhi's position and weather pattern, every winter the city is choked by deadly smog.

Farmers like Paramjeet Singh say they understand inhabitants' health concerns but consider stubble burning a "necessary evil" in the race to clear fields for fresh crops.

POLLUTION CLOUDS

"The smoke is also bad for our eyes and lungs but we don't have the money to buy machines that can clear the crop residue," Singh told AFP in Saneta village, about 230 kilometres (145 miles) northwest of Delhi, in Punjab state.

"And why go after only farmers? There are so many polluting industries in Delhi and Punjab but only we get blamed," said the 42-year-old.

According to state air quality monitors, farm fire smoke accounted for 56 percent of Delhi's pollution in 2018 and 44 percent last year.

Authorities say the share has fallen further this year, but not enough to ease the crisis in Delhi.

Some experts say the worsening smog is because of the number of cars on the roads, construction and industry around the city.

Delhi chief minister Arvind Kejriwal has declared a "war on pollution" putting up billboards across the city while placard-wielding activists urge drivers to turn off their engines when halted at traffic lights.

But experts say political will to tackle pollution is still lacking with central government and Delhi, Punjab and Harayana states unable to agree tough action to clean the air.

And this year farmers, who represent a powerful voting bloc, are upset over new laws they fear will let large private retailers control pricing.

"Yes we are angry and we don't care about the government. Many farmers I know burnt the crop residue mainly to spite the government," said 62-year-old farmer Yashpal Singh.

"If the farmers wanted they could have listened to the government but they chose not to."-AFP