Russia said Tuesday that Syrian government forces had taken control of the city of Manbij, after Damascus deployed troops to the country's north to contain a Turkish offensive.
"The Syrian government army has full control over the city of Manbij and nearby settlements," the Russian defence ministry said in a statement.
Syrian state news agency SANA reported on Monday that government troops had entered Manbij, which is controlled by a military council linked to Syria's Kurds.
Syrian forces moved into the area as part of a deal that has seen regime troops deploy in several Kurdish-controlled areas in Syria's north to protect the region from Ankara's assault.
Russia is a key ally of President Bashar al-Assad and launched a military intervention in 2015 in support of his forces.
The defence ministry said Russian forces were continuing to patrol border areas along the "line of contact" between Syrian and Turkish forces.
"Cooperation has been organised with the Turkish side," it said.
Moscow's special envoy on Syria, Alexander Lavrentyev, said Tuesday that it would not allow clashes between Turkish and Syrian forces.
"This would simply be unacceptable.... And therefore we will not allow it, of course," Lavrentyev, who was on a visit to the United Arab Emirates, was quoted as saying by Russian news agencies.
He said Turkish and Syrian officials were in contact to avoid any conflict.
"Negotiations are taking place in real time," he said.