Swaraj Abhiyan leader Yogendra Yadav was detained in Tiruvannamalai on Saturday when he was on his way to express solidarity with farmers protesting against the proposed Salem-Chennai Expressway project, police said.
Yadav and some others were detained at Chengam in this district, they said without elaborating.
The Swaraj Abhiyan leader tweeted that he was 'manhandled' and pushed into a police van.
'We came on the invitation of Movement Against 8Lane Way. We were prevented from going to meet farmers, phones snatched, manhandled and pushed into police van. Firsthand experience of police state in TN,' he said.
Yadav said he had come for conducting a fact finding about acquisition when he was stopped from proceeding.
In another tweet, he said he had been lodged with some others in a marriage hall.
The Rs 10,000 crore eight-lane expressway connecting Salem and Chennai is being opposed by a section of farmers and landowners who do not want to part with their land.
Dravida Munnetra Kazhagam leader M K Stalin has condemned the 'arbitrary detention'.
'The DMK strongly condemns the arbitrary detention of @_SwarajIndia chief @_YogendraYadav who supported farmers affected by #ChennaiSalemExpressway project,' he tweeted.
The 'intolerant' AIADMK (All India Anna Dravida Munnetra Kazhagam) government will pay the price for denying people the democratic right to dissent and protest, Stalin added.
The project, a central government initiative being implemented by the Tamil Nadu government, aims to bring down the travel time between Salem and Chennai.
The state government has been insisting that it will also help address the issue of fatal accidents on this stretch, besides saving on fuel and vehicular wear and tear.
Chief Minister Edappadi K Palaniswami said compensation being offered to landowners was more compared to the past, as the guideline value has increased.