Russia sent large reinforcements to the city of Qamishli (northeastern Syria), including about 500 soldiers, heavy weapons, armored vehicles and helicopters.
Russia said that it sent more military police to an area in northern Syria that witnessed clashes between Turkish-backed militants and Kurdish forces, near a strategic road in which Russian and Turkish forces carry out security patrols.
And Anadolu Agency quoted local sources as saying that dozens of cargo planes carrying Russian soldiers and Syrian militias landed in the past few weeks at Qamishli airport, coming from the Hmeimim base (in the west of the country).
The sources added that the reinforcements included about 500 Russian soldiers of various ranks, and about 1,300 members of the local militia.
The reinforcements also included hundreds of armored vehicles, 6 helicopters and two Sukhoi Su-27 warplanes.
These developments come before talks to be held in Russia on Tuesday between Russian Foreign Minister Sergey Lavrov and his Turkish counterpart, Mevlut Cavusoglu.
The Syrian file will be among the topics that the two ministers will discuss.
Turkey supports armed groups opposing Syrian President Bashar al-Assad, while Russia supports the forces loyal to him.
Fights broke out between Turkish-backed fighters and Kurdish forces near Ain Issa (northern Syria) this month.
Ain Issa is located on the M4 highway, which links major Syrian cities.
A senior source in the Turkish Defense Ministry said that Ankara would use tomorrow's meeting Tuesday to push for its demand for the withdrawal of the Syrian Kurdish People's Protection Units, which it describes as a terrorist organization.
The People's Protection Units (YPG) is a major military component of the Syrian Democratic Forces coalition, which receives Western support, while Ankara says it represents the Syrian front for the PKK in Turkey.
Mutual arrests
On the other hand, the past two days witnessed mutual arrests between the Syrian regime forces and the Kurdish Protection Units in the city of Qamishli, which ended with a Russian intervention and an exchange of detainees between the two sides, according to Anadolu Agency.
The agency reported - quoting local sources - that the two sides stood up after the mutual arrests, until the Russian officers intervened, and pushed the two parties to release all the detainees on Sunday night.
Qamishli is witnessing from time to time tensions between the regime forces and the elements of the Protection Units, and mutual arrests sometimes turn into clashes, as the Russians intervene in most of these cases and impose calm on both sides.