The so-called Syrian Observatory for Human Rights said on Wednesday that the Turkish reinforcements had entered Syrian soil over the last 24 hours and headed in the direction of the town of A'zaz, which has been seized by Ankara-backed militants.
The regions to the south of the town are currently in the hands of the Kurdish People's Protection Units (YPG).
The observatory said the fresh Turkish deployments are aimed at bolstering Turkish forces who plan to launch an offensive against the YPG which Ankara deems as the Syrian branch of the militant Kurdistan Workers' Party (PKK), which has been battling to establish an autonomous region inside Turkey since 1984.
"Turkish forces are now inside Syria... the forces are huge reinforcements that have been entering since last night,” said a member of one the militant groups backed by Turkey.
The YPG is currently the dominant force behind the so-called Syrian Democratic Forces (SDF) currently engaged in operations aimed at liberating Raqqah – Daesh’s remaining stronghold in Syria.
In August 2016, Turkey began a unilateral military intervention in northern Syria, code-named Operation Euphrates Shield, sending tanks and warplanes across the border, Presstv reported.
Ankara claimed that its military campaign was aimed at pushing Daesh from Turkey's border with Syria and stopping the advance of Kurdish forces, who were themselves fighting Daesh.
Turkey officially ended its military campaign in northern Syria in March 2017 but did not rule out the possibility of yet another act of military intervention inside Syria, which has been gripped by deadly foreign-sponsored militancy since 2011.