State-run agencies have bought 11.92m tonnes of wheat from farmers so far this season, down 25% on the 15.92m tonnes bought in the same period a year ago
Senior police officer MS Bhatia said the deaths occurred after "hundreds" of villagers attacked policemen in Hazaribag district of India's eastern Jharkhand state.
At first police used tear gas and rubber bullets, but were forced to open fire when protests intensified, Bhatia added.
Police said five villagers and seven policemen had also been injured during the clashes.
Villagers have been protesting for several days against a mining site run by NTPC. They have been demanding better compensation and jobs in return for land that was acquired.
NTPC could not immediately be reached for comment.
Conflicts over land rights often erupt in India as the country seeks more land for industrial and development projects.