At least 25 people, including women and children, lost their lives after Russian jets carried out aerial bombings in the northwestern Syrian city of Idlib on Monday.
Al Jazeera reported that the military offensive carried out by Russian Sukhoi jets and the Syrian Army in the rebel-held territory also knocked down schools and medical centres in the region.
The offensive that has lasted since the past few weeks despite being part of a buffer-zone deal has led to the displacement of nearly three million inhabitants of the region.
Russian jets were also behind several raids carried out in Khan Sheikhoun, Kafr Battikh, and several other villages, killing at least 12 civilians last month.
Authorities told Al Jazeera that the aerial campaign launched by Russia at the end of April has killed over 1,500 people since then.
The Russian-backed offensive has so far failed to make major inroads into rebel territory in northern Hama and southern Idlib provinces, where the Islamic State (ISIS or ISIL) is putting up fierce resistance in their last remaining bastion in Syria.
However, Moscow and the Syrian army have repeatedly denied allegations of indiscriminate bombing of civilian areas or any campaign to paralyse the daily life in rebel-held areas.
Russia has blamed the terrorist group for breaking a truce by hitting government-held areas and said Turkey has failed to live up to its obligations under a deal brokered last year that created a buffer zone in the area that obliges it to push out rebels.
According to the United Nations, nearly half of the estimated three million inhabitants in northwest Syria - including Idlib province and parts of neighbouring provinces - had already fled the fighting and moved to areas near the border with Turkey.
( With inputs from ANI )