UN human rights experts call on the Iranian government to release Washington Post correspondent Jason Rezaian immediately.

“The arrest, detention and secret trial of Mr. Rezaian violate his rights and intimidate all those working in the media in Iran,” said David Kaye, the U.N. special rapporteur on freedom of opinion and expression, in a statement Friday.

“His continued detention violates basic rules that not only aim to protect journalists, bloggers, human rights activists and others, but to guarantee everyone’s right to information,” he said.

Rezaian was arrested in Tehran on July 22, 2014 and has been imprisoned in Iran for more than one year. He is charged with a number of offences, including espionage, and could face up to 20 years in prison.

“Mr. Rezaian seems to have been detained for the simple fact of having exercised his rights to freedom of expression, association and political participation,” said human rights expert Seong-Phil Hong, who currently heads the UN Working Group on Arbitrary Detention. “His rights to legal counsel of his choice and to due process of law seem to have been forgotten.”

UN Special Rapporteur on the situation of human rights in Iran, Ahmed Shaheed, reminded the Iranian Government of its responsibility to ensure that journalists do not face prosecution for exercising their professional activities: “Mr. Rezaian’s case is part of a broader crackdown on freedom of expression in Iran. Journalists must be protected, not harassed, detained or prosecuted,” he stressed.

Four closed-door hearings have been held in Rezaian's trial. A verdict could come already this week.