NEW DELHI -- Tens of thousands of farmers marched, rode horses and drove tractors into India's capital on Tuesday, breaking through police barricades to storm the historic Red Fort -- a deeply symbolic act that revealed the scale of their challenge to Prime Minister Narendra Modi's government.

As the country celebrated Republic Day, the long-running protest turned violent, with farmers waving farm union and religious flags from the ramparts of the fort, where prime ministers annually hoist the national flag on the country's August independence holiday. Riot police fired tear gas and water cannons and set up barricades in an attempt to prevent the protesters from reaching the centre of New Delhi, but the demonstrators broke through in many places.

People watched in shock as the takeover of the fort, which was built in the 17th century and served as the palace of Mughal emperors, was shown live on hundreds of news channels. Protesters, some carrying ceremonial swords, ropes and sticks, overwhelmed police.

The farmers have been staging largely peaceful protests for nearly two months, demanding the withdrawal of new laws that they say will favour large corporate farms and devastate the earnings of smaller scale farmers.

The contentious legislation has exacerbated existing resentment among farmers, who have long been seen as the heart and soul of India but often complain of being ignored by the government. As their protest has gathered strength, it has rattled the government like never before since they form the most influential voting bloc in India and are also crucial to its economy.

"We want to show Modi our strength," said Satpal Singh, a farmer who drove into the capital on a tractor along with his family of five. "We will not surrender."

Leaders of the farmers said more than 10,000 tractors joined the protest, and thousands more people marched on foot or rode on horseback while shouting slogans against Modi. At some places, they were showered with flower petals by residents who recorded the unprecedented protest on their phones.

Authorities used tear gas, water cannons and placed large trucks and buses in roads to try to hold back crowd, including rows upon rows of tractors, which shoved aside concrete and steel barricades. Police said one protester died after his tractor overturned, but farmers said he was shot. Several bloodied protesters could be seen in television footage.

Farmers -- many of them Sikhs from Punjab and Haryana states -- tried to march into New Delhi in November but were stopped by police. Since then, unfazed by the winter cold and frequent rains, they have hunkered down at the edge of the city and threatened to besiege it if the farm laws are not repealed.

"We will do as we want to. You cannot force your laws on the poor," said Manjeet Singh, a protesting farmer.

The government insists that the agriculture reform laws passed by Parliament in September will benefit farmers and boost production through private investment. But the farmers fear it will leave those who hold small plots behind as big corporations win out.

The government has offered to amend the laws and suspend their implementation for 18 months. But farmers insist they will settle for nothing less than a complete repeal and plan to march on foot to Parliament on Feb. 1.

Farmers are the latest group to upset Modi's image of imperturbable dominance in Indian politics.

Since returning to power for a second term, Modi's government has been rocked by several convulsions. The economy has tanked, social strife has widened, protests have erupted against laws some deem discriminatory and his government has been questioned over its response to the coronavirus pandemic.

In 2019, the year that witnessed the first major protests against his administration, a diverse coalition of groups rallied against a contentious new citizenship law that they said discriminated against Muslims.

But the latest protests -- which began in northern states that are major agricultural producers -- have triggered a growing farmer rebellion that is fast spreading to other parts of the country, presenting a serious challenge to Modi's government.

Agriculture supports more than half of the country's 1.4 billion people. But the economic clout of farmers has diminished over the last three decades. Once producing a third of India's gross domestic product, farmers now account for only 15% of the country's $2.9 trillion economy.

More than half of farmers are in debt, with 20,638 killing themselves in 2018 and 2019, according to official records.

Devinder Sharma, an agriculture expert who has spent the last two decades campaigning for income equality for Indian farmers, said they are not only protesting the reforms but also "challenging the entire economic design of the country."

"The anger that you see is compounded anger," Sharma said. "Inequality is growing in India and farmers are becoming poorer. Policy planners have failed to realize this and have sucked the income from the bottom to the top. The farmers are only demanding what is their right."

Modi has tried to dismiss the farmers' fears as unfounded and has repeatedly accused opposition parties of agitating them by spreading rumours.

The protests overshadowed Republic Day celebrations, in which Modi oversaw a traditional lavish parade along ceremonial Rajpath boulevard displaying the country's military power and cultural diversity. Authorities shut some metro train stations, and mobile internet service was suspended in some parts of the capital, a frequent tactic of the government to thwart protests.

The parade was scaled back because of the pandemic. People wore masks and adhered to social distancing as police and military battalions marched along the route displaying their latest equipment.

Republic Day marks the anniversary of the adoption of the country's constitution on Jan. 26, 1950.

Police said the protesting farmers broke away from the approved protest routes and resorted to "violence and vandalism."

The group that organized the protest, Samyukt Kisan Morcha, or United Farmers' Front, blamed the violence on "anti-social elements" who "infiltrated an otherwise peaceful movement."

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AP video journalist Rishabh R. Jain contributed to this report