Thousands of Indian farmers entered the historic Red Fort complex in the capital on Tuesday (January 26), one even swinging from a flag pole to the sound of cheers, as violence escalated elsewhere.
The farmers are angry about new laws that they say help large private buyers at their expense.
Protesters also charged at the police with sticks who, in turn, used their batons and tear gas shells to disperse them.
Video footage appeared to show protesters surrounding an unidentified body, cloaked in flags.
The clashes were preceded by a convoy of tens of thousands of farmers driving their tractors through the fringes of the city.
Hundreds, some on horseback, broke away from the main route approved by police to head for central Delhi.
They spoke of wanting to reach the capital to get their message to Prime Minister Narendra Modi:
"We are going to Delhi to answer the call of our leaders to participate in a tractor rally. This law is like poison to us, we are not going to accept it in any condition. We request that Modi takes back the laws as soon as possible."
The protest coincided with India's Republic Day, and threatened to overshadow the annual military parade.
For almost two months, the farmers have been camping outside New Delhi in protest of the agricultural reforms.
Agriculture employs about half of India's population of 1.3 billion, and unrest among an estimated 150 million landowning farmers worries the government.
The protests pose one of the biggest challenges to Prime Minister Narendra Modi since he came to power in 2014.
Nine rounds of talks with farmers' unions have failed to end the protests.
And farm leaders have rejected the government's offer to delay the laws for 18 months, making a push for repeal instead.