Under cover of Russian air power, Assad's forces have made progress around the second city of Aleppo and in southern Syria where Western-backed forces have held out for four years.
Last week, government troops also recaptured Salma, a town that held out for three years as a rare rebel stronghold in the coastal Latakia province.
Amnesty International said last month that Russia had "directly attacked" civilians in opposition-held areas before falsifying evidence to escape blame for possible war crimes.
But in interviews with The Daily Telegraph, civilians attested otherwise. In Idlib province, doctors spoke of multiple bombing raids on the area's last remaining health facility.
In the besieged Damascus suburb of Douma, teachers said their schools had been forced to close after Russian cluster bombs killed eight children at a local playground.
"They killed my son. And as I mourned for him, they killed my daughter too," said the parent of one of the children killed in that December 13 attack.
Moscow's more muscular role in the conflict has added to doubts about whether peace talks scheduled for next week will take place.