Indian police detained dozens of people during a rare protest at the famed India Gate monument in New Delhi demanding action to curb an annual scourge of toxic air swathing the capital and its surrounding region.

Sunday's protest by crowds of all ages holding banners and chanting slogans before police bundled them away was a scarce event, even though Delhi and the national capital region have battled such fumes every winter for years.

“We have only one problem, and that is of clean air,” said Neha, a mask-wearing protester, who gave only one name.

“This problem has been going on for many years but no action is being taken,” she told news agency ANI, in which Reuters has a minority stake.

Visuals from the agency showed police dragging protesters, some holding banners that read, “Breathing is killing us,” while others chanted slogans such as “Our right, clear air” into waiting buses before they were driven away.

The city's air quality index of 345 on Monday ranked as 'very poor', compared to ratings of 'good' in the category from zero to 50, and 'severe' in the range from 401 to 500, according to the Central Pollution Control Board.

Police had called for the spot to be vacated as it was not a designated protest site, they told reporters earlier, while opposition leaders criticised the removal of the protesters.

“The right to clean air is a basic human right,” Rahul Gandhi, leader of the Congress party that has ruled India for much of its history as an independent nation, said on X.

“The right to peaceful protest is guaranteed by our constitution. Why are citizens ... peacefully demanding clean air being treated like criminals?”

The Delhi government was taking steps to prevent pollution, said its environment minister, Manjinder Singh Sirsa.

“We will continue every possible effort to rid us of pollution,” he said in a statement from BJP Delhi on X. “This is the resolve of our government.”

The state government is formed by Prime Minister Narendra Modi's ruling Bharatiya Janata Party.

Winter shrouds the region in a thick haze as cold, heavy air traps construction dust, vehicular emissions, and smoke, bringing respiratory illnesses for many.

Authorities' cloud seeding efforts last month to trigger artificial rain and cut pollution levels failed to produce any rainfall.