Indian security forces deployed tear gas to halt thousands of protesting farmers demanding minimum crop prices from advancing towards New Delhi, following unsuccessful negotiations with the government.

Indian security forces fired tear gas on Tuesday to stop thousands of farmers demanding minimum crop prices from marching on the capital New Delhi after talks with the government failed.

Local broadcasters showed thick clouds of tear gas fired to disperse protesters near Ambala, about 200 kilometres (125 miles) north of the capital, with police also dropping canisters from the air by drones.

Police have set up a fearsome blockade of metal spikes, cement, and steel barricades on the highways from three surrounding states leading to New Delhi.

"Maximum numbers have been deployed," Ranjay Atrishya, assistant commissioner of Delhi Police, told AFP.

Public gatherings of more than five people have been banned in the city.

Farmers in India have political heft due to their sheer numbers, and the threat of renewed protests comes ahead of national elections likely to begin in April.

Two-thirds of India's 1.4 billion people draw their livelihood from agriculture, accounting for nearly a fifth of the country's GDP, according to government figures.

Farmers have called for a "Delhi Chalo", or "March to Delhi", echoing January 2021 when farmers breached barricades and marched into the city on Republic Day during their then year-long protest.

- 'Protest will continue' -

"The farmers are peaceful, but tear gas is being used against us through drones," Sarwan Singh Pandher, a top farmers' union official from Punjab, told reporters.

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Police have set up barricades on multiple highways leading from New Delhi to block thousands of protesting farmers / © Sajjad HUSSAIN/AFP

"The protest will continue till the government agrees to our demands."

Indian broadcasters showed columns of hundreds of tractors moving towards the capital from the surrounding states of Punjab, Haryana and Uttar Pradesh, with some using their machines to drag barricades off the roads.

Where roads could not be cleared, farmers in tractors have sought to head across the countryside.

An AFP photographer saw police close roads at Ghazipur on the outskirts of Delhi, using multiple lines of blockades. A first line of defence using razor wire was set up, then metal barriers, concrete blocks and finally police buses.

Police in Haryana state, adjoining Delhi, said they had made "strong arrangements", adding in a statement that the situation is "under control".

- 'Listen to the farmers' -

The farmers are demanding a law to fix a minimum price for their crops, besides a clutch of other concessions including waiving off loans.

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A security officer stands guard at a road block / © Sajjad HUSSAIN/AFP

"The government should listen to the farmers instead of using tear gas shells and guns against them," said Randeep Surjewala, an opposition Congress MP from Haryana, where many of the protesting farmers come from.

Protests by farmers against agricultural reform bills in November 2020 lasted for more than a year, forming the biggest challenge to Prime Minister Narendra Modi's government since it came to power in 2014.

Tens of thousands of farmers then set up makeshift camps, with at least 700 people killed during the protests.

In November 2021, a year after protests began, Modi pushed through parliament the repeal of three contentious laws that farmers claimed would let private companies control the country's agriculture sector.

Thousands of Indian farmers die by suicide every year because of poverty, debt and crops affected by ever-more erratic weather patterns caused by climate change.