Activist websites have not explained the unprecedented development. Some have suggested dissent within the armed forces, or even a mutiny. The BBC's Jim Muir - reporting from Beirut - says, at the moment, it does look like there is some armed resistance going on, and there are reports the town is bracing for an onslaught by Syrian forces.

Amid conflicting accounts of what really happened - and with no foreign journalists being allowed in to verify the claims - the BBC compares the different versions of events.