Raqqa was captured two years ago by US troops and their YPG/PKK allies but since US President Trump abruptly ordered a pull-out in October, Moscow has swiftly advanced into that territory.
Russian forces have entered Raqqa, the former de facto capital of Daesh, in one of the starkest examples yet of how Moscow has filled the vacuum created by President Donald Trump's decision to pull US forces from northern Syria.
Russian troops were shown in footage on the defence ministry's Zvezda TV channel shaking hands with Syrian children and unloading humanitarian aid bundles with the slogan "Russia is with you" from the back of trucks.
Raqqa was captured two years ago by US troops and their YPG/PKK allies in the biggest victory of Washington's campaign against Daesh in Syria.
But since Trump ordered a pull-out in October, Moscow has swiftly advanced into territory where US troops had operated.
Russia, a close battlefield ally of Syrian regime leader Bashar al Assad, was invited by the YGP/PKK into Raqqa. The terror group controlled the territory after Trump pulled his forces out of the way of a Turkey's anti-terror operation.
Ankara wants YPG/PKK terrorists to be removed from the region, to safeguard the Turkish-Syrian border.
The YPG is the Syrian offshoot of the PKK terrorist organisation.
Russian troops in Raqqa were handing out humanitarian aid and its military doctors were offering residents medical attention, Vladimir Varnavsky, a defence ministry officer, was quoted as saying by RIA news agency.
"Work in the city to get rid of the rubble and clear the area (of bombs or mines) is not yet complete and there is a shortage of clean water, medicine, and food," he said.
Russia last month set up a helicopter base and airport in a northeastern Syrian city and also landed forces at a sprawling airbase in the region that had been vacated by US forces.
Russia and Turkey are carrying out joint patrols along Syria's northern border with Turkey as part of a deal struck between Russian President Vladimir Putin and his Turkish counterpart Recep Tayyip Erdogan.
After saying all US troops would leave northern Syria, Washington has left some behind for now at some bases but rolled back most of their operations.
PKK's 30-year terror campaign has resulted in more than 40,000 deaths, including women and children.
Turkey, the US and the EU recognise the PKK as a terrorist organisation.