Washington Post journalist Jason Rezaian has been convicted by an Iranian court in an espionage case. However, details of the verdict are not known as yet. US-born Rezaian was arrested in July 2014 and has 20 days to appeal against the verdict.

"He has been convicted... but I don't have the details of his verdict," Iran's state-run Isna news agency quoted judiciary spokesman Gholamhossein Mohseni Ejei as saying.

Meanwhile, the journalist's family have alleged that Rezaian's verdict "follows an unconscionable pattern by Iranian authorities of silence, obfuscation, delay and a total lack of adherence to international law, as well as Iranian law. [It is] another sad chapter in his 14-month illegal imprisonment and opaque trial process".

The US State Department, on the other hand, said that there is no concrete information about Rezaian's verdict. "We continue to call for all charges against Jason to be dropped and for him to be immediately released," spokesman John Kirby was quoted as saying.

Martin Baron, executive editor of the The Washington Post said: "This vague and puzzling statement by the government of Iran only adds to the injustice that has surrounded Jason's case since his arrest 15 months ago." According to paper, Rezaian was accused of espionage and collaborating with a hostile government and acting against Iran's national security.

The Washington Post foreign editor Douglas Jehl said that the verdict only "suggests once again that Jason is not really a prisoner, he's a bargaining chip being used by the Iranian government to extract some concessions from the US".

"It's increasingly clear that the final decision about how Jason's case will be handled will be made by political authorities, not by judicial ones," Jehl told Reuters.

Moreover, US President Barack Obama had previously said that Iran has "unjustly detained US citizens", including Rezaian and demanded that he be released.