A man (with head bowed) walks in front of a burning building after a Syrian Air force airstrike in Ain Tarma neighbourhood of Damascus in this January 27th 2013
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What is a barrel bomb? - Explained in 30 seconds

Syria's President Bashar al-Assad has denied in a BBC interview that his forces have used barrel bombs indiscriminately in civilian areas.

He insists that his air force has only targeted "terrorists" and that civilians have not been harmed.

But what are barrel bombs? And why is their use so controversial?

BBC News explains in 30 seconds.

Video produced by Mohamed Madi

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