The move is part of a pilot project to investigate the fate of missing people and release those detained, Ankara says.

The Syrian government and rebel groups have swapped detainees in northern Syria, the Turkish foreign ministry said, describing it as a first step to build confidence between the fighting sides in the war-torn country.

Saturday’s move was part of a pilot project prepared by a working group formed under the so-called Astana process by Turkey, Russia, Iran and the United Nations to investigate the fate of missing people and release those who have been detained, the ministry said.

It did not specify how many people were involved in the swap, but the Syrian Observatory for Human Rights, a UK-based war monitoring group, said rebel factions had released 10 hostages in return for the government releasing 10 detainees.

“Some people who were held in detention in Syria by rebel groups and the regime were set free in the area, under rebel control, of Abu Zindeyn south of al-Bab,” said a written statement from the Turkish ministry.

“The aim is to maintain with new initiatives this practice, which represents an important first step in terms of building confidence between the sides,” it added.

Syrian state news agency SANA said nine men and one woman “were liberated” from the fighters who held them in the Aleppo countryside. A video shared by SANA showed them on a bus, clapping and cheering.

Guarantor powers

Russia, Iran and Turkey have been working together to bring about peace in Syria under what is known as the Astana process, named after the Kazakh capital where the talks take place.

Each country plays a key role in the conflict that started in March 2011. Russia and Iran have intervened on the side of Syria’s government, ensuring its survival, while Turkey supports rebel groups against Assad in northern Syria also to prevent Syrian Kurds establishing and expanding territory along its border.

Various so-called “de-escalation zones” were agreed among the three guarantor powers in Syria as a result of multiple rounds of talks.

The Astana process has gradually come to eclipse a UN-sponsored negotiations framework known as the Geneva process whose participants include the United States and European powers that would be key donors in an international post-conflict reconstruction programme for Syria.