Özcan Keleş, a Turkish origin British barrister, was briefly detained on Monday and is facing possible extradition to Turkey on terrorism charges due to his links to the Gülen movement, which is accused by the Turkish government of masterminding a failed coup attempt in July 2016, according to the Guardian.

Keleş appeared at the Westminster Magistrates Court on Monday accused of spreading propaganda online.

He was subsequently released by the court.

Keleş tweeted on Tuesday that he was deeply offended by the treatment he received from British authorities at the time of his detention on Monday.

“Turkish government is seeking my extradition from UK. I am a British citizen, born and raised here. Charge? Propaganda and membership of a terrorist organization. Home Office certified request. Was arrested, cuffed, held in a cell etc. I am deeply offended. Free speech? No, there is a cost.”

Keleş, who is working on a Ph.D. in the sociology of human rights at Sussex University, is a non-practicing barrister and a member of Gray’s Inn. In 2016, as chairman of the Dialogue Society, he gave evidence to parliament’s foreign affairs select committee about UK relations with Turkey.

The extradition request alleges that Keleş is a member of the Gülen movement, which is designated as a terrorist organization by the Turkish government. The UK does not list it as a terrorist organization.

The movement, inspired by the views of US-based Islamic cleric Fethullah Gülen, strongly denies involvement in any acts of terrorism or the coup attempt.

The extradition papers given to the Crown Prosecution Service (CPS) claim Keleş used his social media accounts to share photos and videos of Gülen as propaganda. Keleş denies all the terrorism allegations.

The Turkish authorities say Keleş would face up to 10 years in prison if convicted of membership of what they describe as an “armed terrorist organization.”

One section of the evidence claims Keleş has visited Gülen, who lives in the US, and that TV images show him walking into a room where Gülen was having his pulse checked.as denied involvement.