Certainly, the circulation by opposition activists of chilling video footage of Friday night's atrocity - blamed on the Assad-supporting Shabiha or "ghost militia" - appears to have ignited unprecedented international revulsion.

Yesterday, the US, France, Britain, Canada, Germany, Italy, Spain, Australia, The Netherlands and Bulgaria expelled Syria's envoys in protest.

While the graphic footage of the outrage might have jolted the world out of its complacency about the low-intensity civil war raging in Syria - more than 10 000 people have already been killed, the majority by Assad's security forces or loyalists - it remains to be seen whether Houla will precipitate Assad's downfall.

Russia has, along with China, twice vetoed UN Security Council resolutions calling for tough action against his regime. On Sunday, Moscow supported a non-binding resolution criticising the use of artillery and tanks in Houla, but its official line is that "all sides" must end the violence, and it is unlikely to support punitive steps against a strategic ally.

It is equally true that the Western powers have little appetite for military intervention because of Syria's strategic location in the powder keg that is the Middle East. Assad's army is far more powerful than that of deposed Libyan dictator Muammar Gaddafi.

So all the world has is UN envoy Kofi Annan's stalled six-point peace plan, which calls for the government to withdraw heavy weapons from towns and cities, followed by a cease-fire and talks with the opposition.

The onus is on the UN, including Russia and China, to compel Assad - and the opposition's Free Syrian Army which is battling his troops - to end the carnage and start negotiating.