Campaigners calling for a Cambridge University student facing the death penalty in South Sudan to be released are staging a 48-hour "cage campaign".
PhD student Peter Biar Ajak, 35, a critic of his country's regime, has been detained without charge since his arrest at Juba Airport in July.
University Amnesty International group members are taking turns inside a cage on the lawn outside King's College.
Chair Tiffany Hui said Mr Ajak had "the interests of his country at heart".
Mr Ajak's lawyer Jared Genser has previously said his client was being "arbitrarily detained in a modern-day hellhole" which was "in clear violation of his rights under international law".
Shortly before his arrest, Mr Ajak had tweeted about South Sudan's "so-called leaders".
He had resettled in the United States as a teenager after being displaced by South Sudan's civil war.
Mr Ajak went on to study at La Salle University in Philadelphia and Harvard University, before moving to Cambridge University.
Returning to his home country on 28 July to hold a youth forum, he was arrested and taken into custody.
The Amnesty Cage Protest has taken place annually at Cambridge for 40 years, and selects a different campaign every time.
Group chair, law student Ms Hui, said it "made sense" to focus on Mr Ajak in 2019 as he is "one of us".
"He was working to try and promote the development of South Sudan," she said.
"His city and university should support that."
A university spokeswoman said the institution remained "deeply concerned about Peter's welfare".
Mr Genser said his client was "being a very effective critic" of the country's current leadership and called for them to step down so that younger people could take over and achieve peace.
A spokesman for the South Sudan government has been approached for comment.