Human Rights Watch (HRW) is calling on Azerbaijani authorities to immediately free Ilkin Rustamzade, an activist who has been in prison for four years.

"The anniversary of his arrest marks another grim milestone in [a] relentless crackdown on critics in Azerbaijan," the New York-based group said in a May 17 statement. "The story of his arrest is as absurd as the charges authorities pressed against him."

Rustamzade, a member of the pro-democracy NIDA youth group, blogger, and critic of the government's human rights record, was arrested on hooliganism charges for alleged involvement in a satirical video that was posted to YouTube, HRW said.

Authorities later charged him with inciting violence and organizing mass disorder in connection with a peaceful protest in 2013.

The 21-year-old university student was sentenced to eight years in prison in May 2014 after an "unfair trial," according to HRW.

Amnesty International recognizes him as a prisoner of conscience.

