The Syrian regime and rebel groups swapped dozens of hostages, including women and children, in Hama province on Tuesday evening, the Britain-based Syrian Observatory for Human Rights and a rebel official said.
The war monitor said that regime representatives and rebels exchanged 112 people, including 24 children, in the rebel-held Qalaat al-Madiq town in rural Hama. Many had been detained for years.
About half of the women were released from regime prisons and then taken to opposition-held areas, the Observatory said.
In return, rebel groups fighting Bashar al Assad's regime released many others, including three unidentified men. The prisoners were shuttled to regime-controlled areas along the coast.
This kind of exchange is rare in the nearly six-year-old war, but has been occurring more often in recent months, the monitor group said.
There was no immediate comment from the Syrian side.
Syria's conflict has killed hundreds of thousands of people, made more than half the country's population homeless, and created the world's worst refugee crisis since World War II.
Mohamad Rasheed, a spokesman for the Jaish al-Nasr rebel group based in Hama, said a civilian committee that negotiates such exchanges with the government oversaw Tuesday's swap.
The prisoners on both sides include children, he said, and "some of the women had given birth while detained."
Most of the hostages released by rebels were from coastal Latakia province, a regime stronghold, and had been held since 2013, Rasheed said.
Some of the prisoners set free by the regime had been detained since the start of the uprising in 2011, he added.