TEHRAN, Iran -- The closed-door trial of Washington Post correspondent Jason Rezaian, who has been detained in an Iranian prison for nearly a year, resumed for a third session Monday, Iran's official IRNA news agency reported. No decision in the case was announced.

The timing of the hearing was noteworthy, coinciding with a push between Iran and world powers to complete a historic deal in Vienna that could impose curbs on Iran's contested nuclear program in exchange for sanctions relief.

Rezaian, 39, is being tried in Revolutionary Court on charges that include espionage and distributing propaganda against the Islamic Republic. U.S. officials, the Post and rights groups have criticized his trial and pressed for his release.

The IRNA report did not immediately elaborate on details of the hearing. The first two sessions in the case were held in May and June.

Mary Rezaian, the journalist's mother, appeared at the courthouse with his wife, Yeganeh Salehi. As in past hearings, they were not allowed inside the courtroom.

The mother said she had no idea whether the timing of the latest hearing had anything to do with the nuclear talks underway in Vienna, nor did she have specific information that the U.S. government was making a fresh push for Rezaian's release as part of a broader deal.

"I do know that there has been effort made on all levels throughout the United States and other countries," she said.

She also expressed hope her son would be released on bail in the coming days, but said his defence lawyer, Leila Ahsan, has not been able to tell the family what happened in the hearing.

Rezaian's brother, Ali, said in an email that the journalist's defence lawyer only recently informed the family that the trial would resume Monday.

He said the documents in Rezaian's case file do not contain valid evidence that he was working against Iran, or that he created or spread propaganda against the country. He also denied that his brother was in touch with senior Iranian officials responsible for security documents, or that he had access to military or nuclear sites.

"We regret that Jason's trial has been closed and his lawyer is barred from discussing the court proceedings," Ali Rezaian said. "Jason's continued detention is as baseless as it is cruel and unjust. We ask the Iranian judiciary to put an end to the delays in his trial, release Jason and allow him to reunite with his family."

Salehi, who is also a journalist, and two photographers were detained along with Rezaian in July 2014 in Tehran. All were later released except Rezaian.

Rezaian is a dual U.S.-Iranian citizen who was born and spent most of his life in the United States. Iran does not recognize other nationalities for its citizens.

Reporters gathered in front of the Tehran courthouse as they have during past hearings but were not allowed inside. Neither Rezaian nor his lawyer was visible to the waiting journalists. Authorities usually bring those charged in sensitive cases through a gate that is closed to the public.

Salehi, a reporter for The National newspaper in Abu Dhabi, and the correspondent's mother, Mary Rezaian, told reporters after the hearing that they were not allowed to attend the session.

Ahsan has previously said Salehi and one of the two unidentified photojournalists also would stand trial. Salehi is barred from travelling abroad.