The buildings, the ones still standing in the Aqraba district of Damascus, are laid open after air strikes on this rebel stronghold.

Even more worrying, according to Human Rights Watch, are reports the bombs contain highly flammable materials like napalm and thermite --- which can cause extreme burns and long term breathing problems --- a violation of the law of war where the aim to deliver a clean and direct kill.

U.S. State department spokeswoman Victoria Nuland.

SOUNDBITE: U.S. State department spokeswoman Victoria Nuland saying:

"And, you can see what the regime is doing in its desperate efforts to forestall the inevitable. It is using increasingly lethal weapons and indiscriminate violence against its people."

Air power --- the ability to swoop in and deliver a targeted attack like this one in the capital -- is President Bashar al-Assad's true advantage against an insurgency that has matched his force on the ground with daring raids and sheer resistance.

Reuters cannot independently verify the content of this video which was posted to a social media website.

In Deir Al Zor, where rebel fighters have taken hold of a military air base, they turned their anti-aircraft guns skyward.