Eight people including four protesting farmers in the northern state of Uttar Pradesh, India on Sunday.
Violence broke out in the Lakhimpur Kheri district during a protest against agricultural reforms.
Images on social media showed vehicles set on fire as people lay covered in blood.
Opposition leaders have been stopped from visiting the families of the victims as the situation remains tense.
Farmers alleged that clashes erupted after federal minister Ajay Mishra’s son drove his car into a group of protesters.
Farmers had assembled in the district to protest against the visit of Mr Mishra and deputy chief minister Keshav Prasad Maurya.
The protesters were angry with Mr Mishra over his earlier statement in which he said the protests involved just “10-15 people” and that “it would take just two minutes to make them fall in line”.
They had been staging a demonstration on the road when the minister’s motorcade allegedly ran over them, killing two protesters and injuring others, farming unions say.
But Mr Mishra has denied the allegations and said his son was not in the car at the time of the incident.
He alleged that farmers threw stones at his vehicle, which led to the driver losing control and ramming into the protesters.
In subsequent violence, three members of the ruling party were and the driver was beaten to death.
Police have confirmed the toll, but have not made any arrests so far. They said the four people who were in the car were among those who died in the violence.
Several prominent farm leaders, including Rakesh Tikait, reached the violence-hit district on Monday. Mr Tikait told the media that farmers will hold discussions with the villagers before deciding their future course of action.
Akhilesh Yadav, former Uttar Pradesh chief minister was stopped from reaching the violence-hit district.
“The prime minister says ours is a vibrant democracy. But stopping opposition leaders from going to Lakhimpur doesn’t really strengthen our democracy. Farmers, who are the backbone of our economy, cannot be treated like this,” he said.
“Their fears are legitimate about private players hurting their income and they should be heard. We need to strengthen our farming systems and not weaken them.”
Senior Congress party leader Priyanka Gandhi was also detained.
Violence in Lakhimpur Kheri marks a dramatic escalation in a 10-month-old protest against agriculture reforms that farmers say will benefit private players at their expense.
Tens of thousands of them have been striking on the outskirts of Delhi since November, demanding that the laws must be repealed.
It is one of the longest farmers-led protests India has ever seen, pitting the community against Indian Prime Minister Narendra Modi.