Shah Faesal, the Kashmiri IAS topper who quit the civil services for politics, was detained at the Delhi airport on Wednesday, reportedly when he was about to fly abroad. He was sent back to Srinagar, where he was placed under house arrest under the Public Safety Act.
Reports suggest he was on his way to Istanbul.
Shah Faesal had been sharply critical on social media about the government's move to end special status to Jammu and Kashmir and split it into two union territories.
Yesterday, he warned on Twitter that Kashmir "needed a non-violent political mass movement" for restoration of political rights.
"Kashmir will need a long, sustained, non-violent political mass movement for restoration of the political rights. Abolition of Article 370 has finished the mainstream. Constitutionalists are gone. So you can either be a stooge or a separatist now. No shades of grey," the 35-year-old tweeted on Tuesday.
Mr Faesal is the latest Jammu and Kashmir politician to be placed under house arrest. Former chief ministers Omar Abdullah and Mehbooba Mufti have been under arrest since August 4, as part of a huge security clampdown to prevent any major backlash following the government's Kashmir decisions. Phone and internet services are still down in the Kashmir Valley and curfew-like restrictions are in place.
In another controversial tweet, Mr Faesal had said: "There is no Eid. Kashmiris across the world are mourning the illegal annexation of their land. There shall be no Eid till everything that has been stolen and snatched since 1947 is returned back. No Eid till the last bit of insult is avenged and undone." He was accused by critics of sedition.
Mr Faesal, an MBBS, quit IAS in January to protest against what he called "unabated killings" in Kashmir and the "marginalization of Indian Muslims". He became the first Kashmiri to top the IAS exam in 2009.