Rahul Gandhi, who is seen as India's prime minister-in-waiting, was briefly arrested after he joined farmers protesting against land being taken over for a $2bn highway, underscoring how land disputes are emerging as a political issue.
Mr Gandhi, general secretary of the Congress Party, was held for two hours in opposition-ruled Uttar Pradesh state then bailed and escorted by police to Delhi.
Mr Gandhi had abandoned his security detail and rode pillion on a motorcycle to Bhatta Parsaul village, where a week-long rally against the highway to the Taj Mahal city of Agra has intensified after police shot dead two protesters.
Mr Gandhi is the son of Congress chief Sonia Gandhi, India's most powerful politician. He has set his sights on resurrecting the Congress Party in time for state polls next year.