Russian forces are acting in support of Syrian government troops who recently deployed around Manbij, in Aleppo province near the border with Turkey.
Kurdish fighters, fearing a Turkish military assault, invited regime forces into Manbij late last month after US President Donald Trump's shock announcement of a full American withdrawal from Syria.
Speaking in a report on Rossiya 24 television, Russian military police spokesman Yusup Mamatov said MPs had started patrolling "the security zone around Manbij."
"The task is to ensure security in the area of responsibility (and) to monitor the situation and movements of armed formations," Mamatov said.
The report said Russian military police would be deployed in the area "on a regular basis."
It showed a group of around a dozen khaki-clad armed military police driving through villages in jeeps and lorries flying the Russian flag.
Critics have warned Trump that an abrupt US withdrawal from Syria would allow allies of President Bashar al-Assad's regime -- including Russia and Iran -- to increase their influence in the country.
About 2,000 US troops, mainly special forces, are deployed in Syria to work with local fighters in the battle against the Islamic State group.
Kurdish fighters formed the backbone of the US-backed Syrian Democratic Forces (SDF), which seized Manbij from ISIS in 2016.
They withdrew from the town earlier this month after Trump's announcement.
Trump has in recent days sought to calm fears of an abrupt US pullout, saying any withdrawal would be done in a "prudent" manner.
It was not clear how close the Russian patrols may have been to areas where US forces are deployed.
Syria's Kurdish minority has largely stayed out of the country's seven-year civil war, but controls large parts of the north and northeast, much of it seized in the US-supported campaign against ISIS.
