UPDATE 1230 GMT: A photograph of the freed Iranians:
Turkey's State news agency Anatolia reports that Syria will release 2130 civilian prisoners, including "many Turkish nationals", in exchange for 48 Iranian men seized by the Syrian opposition last August.
The process has reportedly begun in Damascus, with Turkish and Qatari officials mediating.
The Chairman of Turkey's IHH Humanitarian Aid Foundation, Bulent Yildirim, confirmed the exchange.
IHH has previously asisted in the release of 28 Iranian citizens, seven Syrian, and many Turkish nationals, including journalists Adem Ozkose and Hamit Coskun, from captivity in Syria.
Tehran has always claimed that the 48 Iranian men were "pilgrims". The Free Syrian Army, which released video soon after the abduction, has insisted that the men are connected with the Iranian military, including the Islamic Revolutionary Guards Corps.