More than 80 farmers have been arrested in Punjab for starting fires that contributed to the recent pollution crisis in New Delhi and other cities, officials said Thursday.

Each winter the post-harvest burning of crop stubble covers swaths of the region in toxic smog, which combines with car and factory emissions to turn Delhi into the world's most polluted capital.

The Supreme Court this week ordered a crackdown on illegal stubble-burning, but the fires continued across Punjab and Haryana states -- with many started at night to try and avoid detection.

A senior Punjab police officer said more than 17,000 farm fires had been reported in the state in the past three days, with 4,741 on Wednesday alone.

"More than 84 people have been arrested for violating the law. Cases have been filed against 174 farmers," the officer told AFP.

Punjab and Haryana make up a key agricultural region that produces nearly 18 million tonnes of rice each year. This, in turn, creates nearly 20 million tonnes of crop stubble -- most of which is burnt.

Authorities said more than 48,000 farm fires had been reported in the two states since late September -- a dramatic increase from 30,000 cases in 2018.

The Supreme Court ordered a complete stop to the fires on Monday and on Wednesday slammed local governments for not taking action, instructing them to pay hard-up farmers to stop burning the stubble.

"You just want to sit in your ivory towers and rule. You are not bothered and are letting the people die," said Justice Arun Mishra.

Pollution levels in Delhi remained bad on Thursday, four days after one of its worst pollution attacks in several years during which schools were closed and a public health emergency declared.

Dirty air causes hundreds of thousands of premature deaths across cities each year, according to medical studies.

Tiny particles from the fires, which can enter the bloodstream and penetrate the lungs and heart, get blown over Delhi.

In the winter, cooler temperatures prevent pollutants from dispersing, while smoke from millions of Diwali firecrackers also help turn the capital's skies a putrid yellow.