BEIRUT — More than 2,100 people incarcerated by the Syrian authorities were being released Wednesday in return for 48 Iranians freed by rebels after five months in captivity, Turkish and Iranian officials said, in what appeared to be the biggest prisoner swap since the uprising against President Bashar Assad of Syria began almost two years ago.
The timing of the exchange, brokered by Turkey and Qatar, was notable, suggesting that negotiations over at least some aspects of the Syrian crisis had not been abandoned three days after Assad warned that he would not negotiate with his armed adversaries and dismissed calls for him to quit.
Word of the exchange came as allies of Assad and of his opponents announced that they would continue talking, at least to one another. Lakhdar Brahimi, the special Syria envoy from the United Nations and the Arab League, will meet in Geneva on Friday with senior diplomats from Russia, which has opposed efforts to forcibly unseat Assad, and the United States, which like Turkey supports the armed opposition and wants Assad out.
While Assad’s unbending stance seemed to make a political solution to Syria’s civil war more remote, his only major foreign allies, Russia and Iran, have their eye on maintaining regional influence in a possible post-Assad future, and an interest in ending the Syrian war with state institutions intact. They have made clear they still favor a settlement. Backers of the opposition, too, worry about chaos in Syria and the region as the fight drags on, and the prisoner exchange suggested that Turkey and Iran, at least, wanted to maintain good relations even as they find themselves on opposite sides of the Syrian conflict.
The prisoner exchange came as Brahimi, a veteran Algerian diplomat, made his strongest suggestion yet that he would try to pressure Assad to step aside. Brahimi’s comments, in an interview with the BBC, were his first since Assad, in a rare public address Sunday, appeared to reject Brahimi’s mediation efforts as foreign interference.
The timing of the exchange suggested that negotiations in the Syrian crisis had not stopped.
‘‘In Syria, in particular, I think that what people are saying is that a family ruling for 40 years is a little bit too long,’’ Brahimi said. ‘‘So the change has to be real. It has to be real, and I think that President Assad could take the lead in responding to the aspiration of his people rather than resisting it.’’
Russia and the United States both back Brahimi’s efforts to broker a deal based on an international plan devised in Geneva in June, which envisions a transitional government, but does not spell out the fate of Assad. Talks have faltered in part because Assad’s opponents demand his exit before talks, a precondition Russia rejects as a dangerous interventionist precedent.
Some Middle East political analysts speculated that the timing of the prisoner exchange — and the lopsided ratio of roughly 44 people released by Syria for every freed Iranian hostage — reflected both Assad’s increasing dependence on Iran as well as Iran’s increased pressure on him, possibly out of fear that Syria’s instability may worsen.
“I’m wondering if this is the beginning of Iran starting to cut its losses, pulling out these folks, reducing its presence in the country,’’ said Mona Yacoubian, a senior adviser on the Middle East at the Stimson Center, in Washington.
But some members of the Syrian opposition said the prisoner exchange illustrated merely that Assad showed more concern for Tehran than for his own soldiers, far more of whom are being held in captivity by rebels.
‘‘If only we had half a million Iranians,’’ Adeeb Shishakly, an exile opposition member said on Facebook, ‘‘we would have released them for the freedom of 23 million Syrians.’’
Prime Minister Recep Tayyip Erdogan of Turkey said he hoped the exchange would lead to freedom for more prisoners in Syria — and emphasized that ‘‘This process needs to be appreciated.’’