Russia's defence ministry was quoted by the RIA news agency as saying they would act as "guarantors of law and order" in Douma.
It comes as Russian news agencies reported that Syrian government forces have taken full control of the town, which was the last rebel stronghold in the eastern Ghouta enclave outside the capital Damascus.
"The raised state flag over a building in the town of Douma has heralded the control over this location and therefore over the whole of eastern Ghouta," Major General Yuri Yevtushenko, head of the Russian peace and reconciliation centre in Syria, was quoted as saying.
Douma was the site of an apparent chemical attack by the regime of Syrian President Bashar al Assad that left a reported 70 people dead and 500 more injured at the weekend.
It has sparked the prospect of military action against Assad led by the US and potentially including France and Britain.
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