Turkish combat aircraft performed an airstrike against a SDF base in Syria's Hasakah province, according to local media reports, Trend reports citing Sputnik.
Earlier, Erdogan stressed that a security zone is needed in order to counter "terror threats" coming from the Kurdish PKK party and Syrian Kurdish YPG forces, adding that it would allow for the return of Syrian refugees.
Meanwhile, Washington, which used to support the Kurdish forces in northern Syria, has started to withdraw its troops from the area. The White House said it would not "support or be involved in" Turkey's operation.
On 7 August, Turkey and the United States agreed to create a safe zone in northern Syria after months of tensions between the two countries over the presence of Kurdish militants in the region. Later in August, Erdogan warned that his country could launch a military operation against Kurdish forces in Syria if Washington would fail to meet Ankara's conditions for a safe zone.