Forty-eight Iranians held hostage by rebels in Syria since August have been freed, Iranian state TV reports.
The Iranians were released in exchange for 2,130 prisoners held by the Syrian authorities, a Turkish charity said.
Rebel fighters claimed the hostages had been carrying out a mission on behalf of Syrian government forces.
Iran said a number were retired members of the armed forces, but insisted they were pilgrims who had visited a Shia shrine in the south-east of Damascus.
Officials at the Iranian Pilgrimage and Travel Organization said the group included university students and some public servants.
Shortly after they were seized, the Free Syrian Army’s al-Bara Brigade said it had evidence showing that the Iranians belonged to the Revolutionary Guards and had come to Syria to “serve the regime”.
On Wednesday, a spokesman for the Free Syrian Army, Ahmed al-Khatib, told the AFP news agency that the hostages had been freed.
The Syrian government has not yet confirmed their release and Iranian state TV made no mention of a swap deal.
But earlier, the Turkish Islamic aid organization, Humanitarian Relief Foundation (IHH), said 2,130 civilian prisoners would be released by the Syrian authorities in return for the Iranians.
“Most of the prisoners to be swapped are Syrian citizens in exchange for Iranians, and there are a few Turks as well,” IHH board member Osman Atalay told Reuters news agency.
The head of the agency, Bulent Yildirim, was in Damascus to help co-ordinate the prisoner swap, which was already under way, he added.
The Turkish state news agency, Anadolu, said the deal was brokered by Turkey and Qatar, which have backed the uprising against President Bashar al-Assad, in which the UN says at least 60,000 people have died.
Meanwhile, the UN’s envoy to Syria, Lakhdar Brahimi, will meet top US and Russian diplomats in Geneva on Friday, Russia’s Interfax news agency reports, citing the country’s Deputy Foreign Minister, Mikhail Bogdanov.
The meeting will take place less than a week after President Assad dismissed any chance of dialogue with the opposition in a speech on Sunday, and called on Syrians to fight the “murderous criminals” he claimed were responsible for the violence in their country.
On Monday, a spokesman for UN Secretary General Ban Ki-moon said he had been disappointed that the speech did not “contribute to a solution that could end the terrible suffering of the Syrian people”.
Ban Ki-moon and Lakhdar Brahimi strongly support the peace plan outlined by the Action Group for Syria in June.
The group called for an immediate cessation of violence and the establishment of a transitional government that could include officials serving under President Bashar al-Assad and members of the opposition.
Lakhdar Brahimi has said any plan must also include a “large, robust peacekeeping force” to ensure the ceasefire is observed.