Iran acknowledges captivity of missing former FBI agent Robert Levinson for the first time

In a filing to the United Nations, Iran said the case in its Revolutionary Court over Robert Levinson was "on going", without elaborating.

It was not immediately clear how long the case had been open, nor the circumstances by which it started, but the revelation comes amid a renewed push to find Levinson with an offer of $20 million for information from the Trump administration.

That offer is in addition to $5 million earlier offered by the FBI.

"According to the last statement of Tehran's Justice Department, Mr. Robert Alan Levinson has an on going case in the Public Prosecution and Revolutionary Court of Tehran," the text of Iran's filing to the UN's Working Group on Enforced of Involuntary Disappearances read, according to the Associated Press.

The Revolutionary Court typically handles esponiage cases and others involving smuggling, blasphemy and attempts to overthrow the government.

Westerners and Iranian dual nationals with ties to the West often find themselves tried and convicted in closed-door trials in these courts, only later to be used as bargaining chips in negotiations.

Iran's mission to the UN did not immediately respond to a request for comment and its state media has not acknowledged the case.

Who is Levinson?

Levinson disappeared from Iran's Kish Island in March 2007, where he met with American fugitive Dawud Salahuddin, wanted for the assasination of an Iranian dissident in the US.

For years, US officials insisted that the retired FBI investigator, credited with busting Russian and Italian mobsters, was working for a private firm on his trip.

But in December 2013, the AP revealed Levinson in fact had been on a mission for CIA analysts who had no authority to run spy missions.

His family had received a $2.5 million payment in order to stop a lawsuit revealing the details of his work, while the CIA forced out three veteran analysts and disciplined seven others in response.

Levinson had been presumed to be in Iranian government captivity, but his presence in the country had not been officially acknowledged until now.

Iran in February requested the UN group to close its investigation into Levinson, saying "no proof has been presented by the claimant in this case to prove the presence of the aforesaid in Iran's detention centres".

Since his disappearance, the only photos and video of Levinson emerged in 2010 and 2011. He appeared gaunt and bearded with long hair, and was wearing an orange jumpsuit similar to those worn by detainees at the US prison at Guantanamo Bay.

The video, with a Pashtun wedding song popular in Afghanistan playing in the background, showed Levinson complaining of poor health.

Levinson is the longest-held hostage in US history.

Follow us Twitter and Instagram to stay connected