Syrian activists say the Daesh terrorist group has killed 33 young men in eastern Syria, close to the border with Iraq.

The Britain-based Syrian Observatory for Human Rights says Daesh members slit the throats of the men, aged between 18 and 25, near the town of Mayadeen in Deir el-Zour province on Wednesday.

The group says it's not clear who the men were and whether they were Syrian troops or rebels.

Opposition activist Omar Abu Laila, who is from Deir el-Zour but currently lives in Europe, also reported the killing.

Daesh has carried out similar killings in Syria this year. When it controlled the ancient Syrian city of Palmyra, Daesh carried out public beheadings, including of the antiquities chief whose body was hung from a pole in a main square.