The military councils of the Syrian Democratic Forces (SDF) on Monday declared a general mobilization in areas under their control in northeastern Syria.
They also announced the sending of military reinforcements near the borders with Turkey as Ankara continues to threaten to carry out a new offensive in the region.
The Syrian Observatory for Human Rights reported the arrival of new regime reinforcements on the frontlines in the Manbij countryside, east of Aleppo.
Several buses loaded with regime and Russian forces arrived at the front lines on Monday.
Pro-Turkish National Army factions in the Manbij countryside have also taken a stand.
Regime forces have recently reinforced their positions in Ain Issa and on the M4 international highway.
Reinforcements included buses carrying 250 soldiers, five tanks and heavy weapons.
The region witnesses almost daily clashes between the warring parties.
Separately, masses of US soldiers roamed the countryside of Tal Tamr, northwest of al-Hasakah governorate, under the protection of SDF patrols.
The international coalition forces and the SDF carried out a new series of live ammunition military exercises at the coalition base in the town of al-Shaddadi, south of al-Hasakah.
A military aid convoy, consisting of 50 trucks, also arrived at the base. It included weapons, logistical equipment, armored vehicles, and water and fuel tanks.
The day before, 80 trucks carrying reinforcements arrived at coalition bases in al-Hasakah and Deir Ezzor province.