Syrian regime and Russian bombing exacerbated the extent of the destruction when Syria was struck by a deadly 7.8-magnitude earthquake that originated in Turkey on Monday, according to a rescue group.
The quake has killed over 2,600 people in the two countries, with almost 1,000 of those lives lost in Syria.
Raed Al-Saleh, the head of the White Helmets civil defence group that operates in opposition-held areas, said bombing carried out by Moscow and the regime of President Bashar Al-Assad made buildings vulnerable.
"The bombing by the [Syrian] regime and Russia during the past years caused structural damage to thousands of buildings and when the earthquake happened, they collapsed," he told °®Âþµº, adding "very poor" infrastructure was also a factor.
"Most of the buildings that were previously bombed or faced air raids collapsed today [on Monday] in the earthquake."
Al-Saleh added the areas most damaged by the tremor in the rebel-stronghold province of Idlib, which borders southern Turkey, were those worst affected by regime and Russian airstrikes.
Asked about this, Laila Kiki, executive director of advocacy group the Syria Campaign, commented on the tremor's impact on Syria's northwest.
She said even though the quake is a natural disaster, the actions of Moscow and the regime have made its consequences "far worse".
"Years of relentless bombardment has damaged infrastructure and left residential buildings at risk of collapse," she told °®Âþµº.
"Russia and the regime's tightening control of cross-border humanitarian aid to the area has also compounded people's suffering.
"The devastation from the earthquake in these areas highlights why it is so important for Russia and the Syrian regime to be held to account for their crimes.
"It should also serve as proof to the international community that it is time to stop Assad and Russia so we as Syrians can rebuild our country."
Amnesty International UK's crisis response manager Kristyan Benedict said some of the "most vulnerable and traumatised people on the planet" live in northwest Syria.
"Many have already endured forced displacement, bombing raids, poverty, disease, hunger, and years of injustice," he told °®Âþµº.
"Health care was already overwhelmed mainly because of Russian and Assad regime campaigns to destroy hospitals and clinics.
"The devastating earthquake compounds what was already a humanitarian catastrophe."
Russia is a key ally of the Syrian regime. Moscow intervened militarily in 2015 on Assad's side in the country's civil war which began over a decade ago.
The conflict has killed hundreds of thousands of people and created millions of refugees.