A Washington Post journalist imprisoned for five months in Iran will be tried by Tehran’s revolutionary court, the nation’s state news agency announced on Wednesday, in a report that did not say what charges he faces.

Police arrested dual Iranian-American citizen Jason Rezaian on 22 July 2014, and in the 175 days since he has lived in a small cell, endured long interrogations, and suffered serious infections and weight loss, his brother Ali told the Guardian in December. The Post’s Tehran bureau chief was detained alongside his wife, who was freed after 10 weeks, and two others who were also eventually released.

Prosecutor Abbas Jafari Dowlatabadi’s announcement of Rezaian’s indictment, as reported by state-owned IRNA, comes a little more than a month after the journalist was formally charged by Iranian authorities. The brief statement simply said that “the case against Jason Rezaian has been referred for processing to Tehran’s revolutionary court”.

Rezaian could now stand trial before Tehran’s special revolutionary court, which deals in cases ranging from espionage and state security to slander against Iran’s supreme leader, Ayatollah Ali Khamenei. The court could also move to review his case, which would keep Rezaian in a state of limbo.

The five charges against Rezaian have not been made public, and may not even be clear to the accused or his lawyer, since the journalist can speak but not read Farsi and has not been allowed a translator. Rezaian’s mother told the Washington Post that Rezaian only knew the allegations pertained to “activities outside the bounds of journalism”. When asked by the New York Times what he knew of the charges, Rezaian’s attorney could only say, “I don’t know what happened.”

Also on Wednesday, the US secretary of state, John Kerry, met the Iranian foreign minister, Mohammed Javad Zarif, ahead of negotiations about Iran’s nuclear programme. Zarif told reporters in Geneva that he hopes for a resolution to the case, “but unfortunately there are judicial issues involved which the judiciary has to deal with”.

Kerry in December denounced Iran for denying Rezaian bail and has called for his release: “I am personally dismayed and disturbed at these reports, as I have repeatedly raised Jason’s case, and other cases of detained or missing US citizens, with Iranian officials.”

The Geneva talks will include the US, France, Germany, Russia, China and the UK, and are part of glacial efforts at rapprochement by Iran’s moderate president, Hassan Rouhani, and western powers.

Rezaian’s wife and mother have been allowed to visit him briefly, according to both Zarif and his brother, and the journalist was allowed a half-hour phone call to his family on Thanksgiving Day. The family has pleaded for his release, including a direct appeal to Ayatollah Khamenei and in a December statement that said the courts had acted “in disregard of Iran’s own laws”.

“This continued disrespect for Iran’s judicial system should be a concern not only to the international community,” the statement continues, “but also to all those Iranians who claim that Iran is a country of laws which should be recognised as such by major world powers.”

Rezaian, accredited as a journalist by Iran’s culture ministry, had renewed his press credentials on the day of his arrest. The Washington Post and other newspapers and press organisations have urged Iran to release Rezaian.

Iran kept 30 journalists imprisoned in 2014, according to the non-profit Committee to Protect Journalists, including several detained after a brief periods of freedom.