An Iranian court on Monday resumed the trial of jailed Washington Post correspondent Jason Rezaian on espionage charges, Iran's semi-official Fars news agency reported.

The first hearing for Rezaian, an Iranian-U.S. citizen, was held behind closed doors on May 26 at Branch 15 of the Revolutionary Court in Tehran. Rezaian has been in Tehran's Evin prison since his arrest in July, 2014.

"The second hearing of Rezaian for spying has started at Branch 15," Fars reported, without elaborating.

Rezaian's lawyer, Leila Ahsan, told Iran's Tasnim news agency after the second hearing: "He has been charged with espionage for collecting confidential information ... and handing it to hostile governments, writing a letter to (U.S. President Barack) Obama and acting against national security".

Rezaian's wife Yeganeh Salehi and a woman photojournalist who were detained with him but were later released also went on trial last month, Iranian media reported.

Obama, relatives and rights groups have called for Rezaian's release and for more information about the charges. Washington has rejected the "absurd" espionage charges against Rezaian.

Rezaian's brother Ali told Reuters Television last month that his brother, the Post's Tehran bureau chief, had lost 40 pounds (18 kilograms) in prison.

Tehran and six world powers, including the United States, are trying to meet a June 30 deadline for a final nuclear deal to end a decade-old standoff with the West.