Away from Ukraine, at least 25 people have been killed after Syrian and Russian jets launched airstrikes on Syrian rebels who are making their way through the country after gaining control of Aleppo.
Russia is already stretched militarily and now it has entered another conflict with its ally Syria, which is being threatened by an insurgency.
In 2015, Russia saved President Bashar al Assad from the brink of collapse during the Syrian civil war.
In return, the Assad regime offered Putin unlimited access to military bases – allowing Russia to extend its influence across a much broader area and providing Putin with a military stronghold in the region.
On Sunday, Russian and Syrian jets struck the rebel-held city of Idlib in northern Syria, military sources said, as Assad vowed to crush insurgents.
Residents said one attack hit a crowded residential area in the centre of Idlib, the largest city in a rebel enclave near the Turkish border where around four million people live in makeshift tents.
At least seven people were killed and dozens injured, according to rescuers at the scene.
The Syrian army has also said dozens of its soldiers had been killed in the fighting in Aleppo.
The rebels, led by jihadi group Hayat Tahrir al Sham, took over most of Aleppo in a shock offensive on Saturday.
The Syrian army and its ally Russia say they target the hideouts of insurgent groups and deny attacking civilians.