Farmer leader Rakesh Tikait was Sunday detained by the Delhi Police at the Ghazipur border while he was trying to enter the national capital to take part in an unemployment protest at Jantar Mantar.
He alleged the Delhi police was working at the behest of the Centre and did not allow him to meet the unemployed youth.
A Delhi Police official said Tikait, the national spokesperson for the Bharatiya Kisan Union (BKU) and a prominent face of the Samyukt Kisan Morcha (SKM), was stopped at the border around afternoon.
"Thereafter, he was detained and taken to Madhu Vihar police station where police spoke to him and requested him to return," Special Commissioner of Police (Law and Order) Dependra Pathak said.
The DCP said Tikait "agreed" with the police request, and was "escorted back".
Several farmer leaders and organisations gathered at Jantar Mantar for their "Rozgar Sansad" (employment parliament) organised by the Samyukt Rojgar Andolan Samiti (SRAS).
The SRAS said in a statement that Tikait, who was coming to participate in the movement, was stopped by the police at the border.
AAP leaders Gopal Rai and Sanjay Singh, and farmer leaders Gurnam Singh Chadhuni and Rishipal Ambavat participated in the protest on Sunday.
Police sources said Tikait was detained as the Delhi police was trying to prevent "undue gathering" in the national capital.
In a tweet in Hindi, Tikait slammed the government, saying "The Delhi Police working at the behest of the government cannot suppress the voice of the farmers. This arrest will bring a new revolution. This struggle will continue till the last breath. Won't stop, won't get tired, won't bow down."
He also accused the Centre of oppressing the unemployed, the youth, farmers and labouers of the country.
"The Modi government is bent on oppression of the unemployed, the youth, farmers and labourers. Be prepared for a long struggle for the fight of rights. At the behest of the Centre, the Delhi Police did not allow (me) to meet the unemployed youth," he said in another tweet later.
Delhi minister and Aam Aadmi Party (AAP) leader Gopal Rai condemned Tikait's detention.
"Farmer leader Rakesh Tikait was on his way to the employment movement but was stopped by the police at the border itself. This is very despicable," Rai tweeted in Hindi.