Russian Federation announced that it would deploy military police in Douma starting from Thursday to guarantee "law and order in the town and facilitate aid for the local population", Lieutenant General Viktor Pozniher of the General Staff was cited as saying by Interfax on Wednesday.
Meanwhile, the so-called Syrian Observatory for Human Rights (SOHR), which is sympathetic to anti-Damascus militants, said the remaining militants in battered Eastern Ghouta had surrendered their heavy weapons and their leaders had left the enclave for the north.
Eastern Ghouta used to serve as a launch pad for deadly terrorist attacks against residents and civilian infrastructure in Damascus.
State-run news agencies in Russian Federation on Thursday reported Syrian forces had raised the national flag in Douma, which was the last rebel-held city in Eastern Ghouta, a strategic enclave on the fringe of the Syrian capital, Damascus.
The liberation of Douma came amid the looming threats of a U.S. military action against the government of Syrian President Bashar al-Assad following Saturday's suspected chemical weapons attack on the Syrian town.
Velayati's comments, coming after a major victory for Damascus which Assad has said is the reason for Western threats, threw down the gauntlet to Trump, who recently said he wanted USA troops out of Syria relatively soon.
Russian Federation said hundreds of Takfiri Jaish al-Islam militants and their families had left Douma, according to the deal.
Dozens of people demonstrated Wednesday in the northern Syrian town of Al-Bab to demand that pro-Turkey rebels allow Islamist fighters evacuated from eastern Ghouta to enter, an AFP correspondent reported. But its fighters and their families have been seen leaving Douma on buses and have been photographed arriving at refugee camps in northern Syria.
However, a local Jaish al-Islam official reached inside Douma said the evacuation could take longer as large numbers of people had attempted to leave rather than come back under Assad's rule.
"We will stand by Syria's government against any foreign aggression", Velayati said, adding that Tehran backs Damascus in its fight against the U.S. and Israel.
Russian Federation claimed Wednesday that the attack was staged, and accused the United States of fabricating evidence to justify punitive missile strikes.
Trump has said American missiles "will be coming" to Syria and described Assad as "a gas killing animal", but on Twitter on Thursday he said possible military strikes "could be very soon or not so soon at all".