It's unclear what this substance is, but some people believe it's white phosphorous, but as yet there's been no evidence of how these bombs have been delivered.
The following video from the Aleppo region shows what I believe is the first evidence of incendiary cluster bombs being deployed in Syria
At first glance these may look like regular RBK cluster bombs, but this image from the video showing the bomb markings tell us exactly what the bomb is
The text reads RBK-250, the cluster canister type, and ZAB-2.5. ZAB stands for zazhigatelnaya aviatsionnaya bomba, meaning "incendiary aircraft bomb". At the end of the video we also see what appears to be the scorched remains of one of the bomblets. As yet it's unclear the exact type of incendiary substances used with the ZAB-2.5 bomblets, so I cannot confirm this is white phosphorus. This clearly indicates that there's at least one incendiary cluster bomb in this, picture, and three if the tail fins belong to RBK-250 ZAB-2.5 cluster bombs.
As with all cluster bombs we'll almost certainly see more evidence of cluster bomb canisters and unexploded bomblets, so expect more videos like this in the future. It's also interesting to note that this bomb appears shortly after the recent significant gains by the Syrian opposition across the country, much like cluster bombs began to appear after the Damascus-Idlib highway was captured near Maarrat al-Numan in Idlib.
Update December 16th Nic Jenzen-Jones has put up a couple of great posts on his blog detailing the contents of the ZAB bomblets (a variety of thermite mixes), and a guide to telling the difference between white phosphorous and thermite munitions, both highly recommended reads.
Heavy Weapons And Surface To Air Missiles Captured From The 46th Regiment Base
Video Shows Captured SA-16 And SA-24 Surface To Air Missiles
Unexploded Cluster Bomblets Repurposed As DIY Rocket Warheads
Unexploded Bombs Used In A Truck Bomb By Jabhat al-Nusra
Clear Evidence Of DIY Barrel Bombs Being Used By The Syrian Air Force
Cluster Bomb Usage Rises Significantly Across Syria
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