The Syrian military and its ally Russia conducted deadly joint air raids on areas under Islamist-led rebel control on Monday, as they battle a lightning offensive that has wrested swathes of Syria from government control.

Russia said on Wednesday that it strongly backs the actions of the Syrian leadership to counter an offensive by what it said were terrorist groups receiving support, including drones and training, from outside the country.

Syria's civil war has taken a dramatic turn, with dictator Bashar Assad once again leaning on Russian support after a shock offensive by Islamist rebels in Aleppo.

Opposition supporters are ecstatic but others are wary of their new Islamist rulers as Assad regime begins counteroffensive

Images shared on social media have illustrated the anger that Syrian rebels fighting President Bashar al-Assad feel toward his ally Vladimir Putin. The Russian leader has been indispensable in propping up Assad's regime during the brutal Syrian civil war that started in 2011 but has been essentially frozen over the last four years.