Further signs that the Syrian conflict is spreading across the region are certainly alarming. But the dangers of an over-reaction from the international community are hardly less of a risk.
Although the Assad regime swiftly condemned the fatal car bomb in the Lebanese capital of Beirut on Friday, few doubt that the attack bore Damascus's fingerprints. The assassinated security chief, Major General Wissam al-Hassan, was behind last month's arrest of a Lebanese associate of the Syrian President; and both Bashar al-Assad and his father have, for decades, used political violence in their dealings with their weaker neighbour.
The explosion in Beirut is no isolated case of contagion. Taken together with arrests in Jordan of would-be bombers with arms from Syria, exchanges of fire over the Turkish border, and fighting between Sunnis and Alawites in northern Lebanon in August, predictions of imminent regional conflagration start to look all too prescient.
It is as well not to be precipitous, though. For Damascus, attempts to export the conflict have the dual attraction of distracting attention from domestic atrocities and adding to the message that, were the regime to fall, the result would be worse still. But that does not make general sectarian meltdown a foregone conclusion.
Nor has international intervention much hope of averting it. With no end to the conflict in sight, however, and UN efforts to broker peace ever more threadbare, calls for action are growing louder. And with the US election two weeks away, Barack Obama under fire for "weakness" on the Middle East, and the real prospect of a Republican in the White House, the pressure to "do something" will only increase.
The danger of instability spreading from Syria is, of course, a genuine one; and with more than 25,000 dead, the human toll of Assad's intransigence is already appalling. But one bomb in Beirut does not necessarily spell the start of regional catastrophe. Amid the wreckage, what is needed, above all, is caution.