The bus, traveling to Tehran, Iran's capital, from Urmia Lake, and carrying over 20 reporters and media workers, overturned near the city of Naqadeh on its way back from a environmental press trip organised by the government.
Islamic Republic News Agency (IRNA) correspondent Reyhaneh Yassini and Iran Students News Agency (ISNA) reporter Mahshad Karimi lost their lives in the crash.
Twenty-one other journalists were injured in the accident, including four who are in a critical condition and were taken to Urmia city hospital.
According to media reports, the commander of the country's traffic police announced after the crash that the bus was out of order and belonged to a cement factory. Some of the journalists who were rescued from the bus complained to IJA that the condition of the bus was inappropriate for this trip.
The IJA said: "We will investigate the incident and its causes, and if there is any negligence on the part of the relevant institutions in the incident, we will pursue it vigorously and will duly inform the public."
IFJ General Secretary said: "Two journalists have unfortunately paid the highest price for doing their job and we are extremely shocked by their loss. We wish the wounded journalists a swift recovery and send our deepest condolences to the family and colleagues of ReyhanehYassini and Mahshad Karimi. We call on the Iran autorities to conduct a full investigation into the bus crash."