DUBAI, Nov 22 (Reuters) - An Iranian court has sentenced Washington Post reporter Jason Rezaian to a prison term, the state news agency said on Sunday quoting the judiciary spokesman, a case that is a sensitive issue in contentious U.S.-Iranian relations.

The length of the prison term was not specified. "Serving a jail term is in Jason Rezaian's sentence but I cannot give details," judiciary spokesman Gholamhossein Mohseni Ejei told a weekly news conference in Tehran, according to IRNA.

In Washington, U.S. State Department spokesman John Kirby told reporters he was aware of the IRNA report but could not independently confirm it. It was not immediately clear why Iran has not given details of the ruling against the 39-year-old Rezaian, who Iranian prosecutors accused of espionage.

On Oct. 11, Ejei said Rezaian, the paper's Tehran bureau chief who has both U.S. and Iranian citizenship, had been convicted, without elaborating. He said then that Rezaian had 20 days to appeal against the verdict.

The Washington Post said last month that the verdict, issued soon after Iran raised hopes of a thaw in its relations with the West by striking a nuclear deal with world powers includingWashington, was "vague and puzzling."

It said the vagueness of Ejei's remarks showed Rezaian's case was not just about espionage and that the reporter was a bargaining chip in a "larger game." The Post and his family denounced the espionage charges against Rezaian as absurd.