The Washington Post on Monday angrily denounced the conviction of one of its reporters in a secret Iranian court, calling the proceeding an "outrageous injustice."

Washington Post Executive Editor Martin Baron criticized Iran’s conviction of Post reporter Jason Rezaian in a closed-door trial on charges that are unclear, saying the verdict was unconscionable.  

Rezaian was found guilty of various allegations by an Iranian court, the country's state TV reported late Sunday.

"Iran has behaved unconscionably throughout this case, but never more so than with this indefensible decision by a Revolutionary Court to convict an innocent journalist of serious crimes after a proceeding that unfolded in secret, with no evidence whatsoever of any wrongdoing. For now, no sentence has been announced," Baron said in a statement Monday.

It was not immediately clear of what exactly Rezaian had been convicted. He had faced multiple charges, including espionage, at his trial, which was widely criticized by the U.S. government and press freedom organizations.

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Rezaian reportedly faces up to 20 years in prison if convicted on all charges.

Baron reiterated the Post's position that Rezaian is innocent and that he should be exonerated and set free.

The U.S. State Department, which has not had formal diplomatic relations with Iran since the 1979 hostage crisis, yet recently completed negotiations on a deal lifting economic sanctions in Iran, was awaiting confirmation that Rezaian had been found guilty.

“We continue to closely track the news coming out of Iran concerning the trial of U.S. citizen Jason Rezaian," said State Department spokesman John Kirby. "We’ve seen news reports that Jason has been convicted, but we still have not seen any official confirmation of a verdict on specific charges or any further information. Unfortunately, this is not surprising given that this process has been opaque and incomprehensible from the start. Regardless of whether there has been a conviction or not, we continue to call for the government of Iran to drop all charges against Jason and release him immediately."

But Iranian judiciary spokesman Gholam Hossein Mohseni Ejehi told state TV Sunday that the journalist had been convicted.

"He has been convicted, but I don't have the verdict's details,” Ejehi told state TV Sunday." Ejehi added that Rezaian and his lawyer are eligible to appeal the conviction within 20 days.

Ejehi discussed Rezaian's case during a press conference earlier Sunday that was restricted to Iranian media. Initial Iranian media reports, which quoted Ejehi as saying that a verdict has been issued, didn't include any comment that Rezaian had been convicted -- leading to confusion surrounding the decision.

Only the semiofficial ISNA news agency eventually reported the conviction comment, and later in the day state TV broadcast Ejehi's comment that Rezaian has been convicted. State TV aired selected video of the press conference and called Rezaian an "American spy."

The paper is working with Rezaian's family and legal counsel to swiftly appeal the verdict and push for his release on bail pending a final decision, Baron said.

"The contemptible end to this `judicial process' leaves Iran's senior leaders with an obligation to right this grievous wrong. Jason is a victim -- arrested without cause, held for months in isolation, without access to a lawyer, subjected to physical mistreatment and psychological abuse, and now convicted without basis. He has spent nearly 15 months locked up in Iran's notorious Evin Prison, more than three times as long than any other Western journalists."

Leila Ahsan, Rezaian's lawyer, told The Associated Press Sunday "there are no new developments" and said she has not yet received the verdict. Ahsan was not reachable for comment on Monday.

Rezaian was detained with his wife, who is a journalist for The National newspaper in the United Arab Emirates, and two photojournalists on July 22, 2014. All were later released except Rezaian.

Rezaian, the Post's Tehran bureau chief since 2012, has dual Iranian-American nationality. Iran does not recognize dual nationality for its citizens.

The Associated Press contributed to this report.