Over 70 people were detained on Thursday when they were staging a protest at the Jantar Mantar here in support of Punjab farmers, who are agitating against the Centre's farm laws.
The protestors included members from Left-backed trade unions, the Students' Federation of India. Students from the Jawaharlal Nehru University also participated in the protest.
Over 70 people, including women, were detained and later released, a senior police officer said.
When they gathered at the Jantar Mantar for the protest, they were warned and it was conveyed to them that they did not have the permission to organise the protest, the officer said.
But when they refused to abide, they were detained and taken to a nearby police station from where they were released later, the officer said.
Delhi Police personnel have been deployed in large numbers in border areas of the national capital and all incoming vehicles are being checked in view of the 'Delhi Chalo' march by Punjab farmers against the Centre's farm laws.
Five sand-laden trucks have been stationed at the Singhu border to stop tractors being driven by the protesters, police said.