Hundreds of secret hospitals are operating underground in Syria, treating injured protesters and opposition members, as a brutal crackdown against pro-democracy demonstrators by President Bashar al-Assad's regime enters its eighth month.
Those doctors who agree to treat protesters are themselves being targeted by the regime, and face arrest, torture and even death if they are discovered, a new documentary to be broadcast by Channel 4 reveals.
'Unreported World: Undercover Syria' also shows that the regime is facing a growing number of military defections, as groups of armed soldiers refuse to fire on civilians and join the opposition, leading to a rising tide of violent clashes in what has until now been a peaceful, although brutally repressed, opposition movement.