This killing must not be allowed to unleash conflict across the region

The massive explosion which killed Lebanon's former prime minister, Rafik Hariri, was by far the most destructive attack since the formal end of the civil war 15 years ago. It shattered not only the armoured convoy of Mr Hariri and his entourage, but a peace that had grown increasingly uneasy in a wider region where peace is all too rare.

The massive explosion which killed Lebanon's former prime minister, Rafik Hariri, was by far the most destructive attack since the formal end of the civil war 15 years ago. It shattered not only the armoured convoy of Mr Hariri and his entourage, but a peace that had grown increasingly uneasy in a wider region where peace is all too rare.

A billionaire businessman who had served as prime minister for a total of 10 years, Mr Hariri was seen as a possible unifying figure in a still-fractured country. His political experience, his personal wealth, and his position outside Lebanon's main political and military groupings made him unique. Inevitably, he also made enemies. The manner of his killing, however, suggests that he was the victim less of an individual vendetta than an assassination designed to eliminate the opposition he increasingly represented.

One, hitherto unknown, Islamic group claimed responsibility last night in a video broadcast by al-Jazeera. A more obvious culprit, however, would be Syria - and specifically that strand of Syrian power represented by its secret service in Lebanon. The essential question, however, is less who killed Mr Hariri than whose interests are served by his death. And here it is hard not to agree with Syria's president, Bashar Assad, who described it as a terrorist attack intended to destabilise Lebanon.

Destabilisation, though, can take many forms in the Lebanon of today. A general election is scheduled for April or May, but the rules have yet to be finalised. Last autumn a UN Security Council resolution called for a speedy withdrawal of foreign forces - by which it meant the Syrians - to allow a return to sovereignty and self-government. The scene was set for an election that could have turned on the continued presence of Syria - and might do still. Disorder, it could be argued, would furnish a pretext for the Syrians to remain.

The murder of the one politician who might have been able to bring moderate, nationally-minded Lebanese together, who might have been able to negotiate with Syria about troop withdrawal and who was well-connected abroad, leaves a dangerous vacuum. It also risks unleashing forces that even Syria might not be able to control. Renewed violence in Lebanon, even a return to civil war, could have much wider repercussions.

The extent of President Assad's authority inside Syria is far from certain. Damascus is coming under ever stronger pressure both from the US and Israel: the US which regards it as a base for terrorists and does not trust it to have "learnt the lesson" from Iraq, and Israel, which needs security on its northern border as it plans its withdrawal from Gaza. Instability in Lebanon is one thing; instability in Syria would be quite another. The US has complained about militants infiltrating Iraq from Syria across a porous border; it is not impossible to conceive of circumstances in which they might move in the opposite direction.

Israel may be settling in for serious talks with the new Palestinian government, but this is one of the few hopeful developments in the region. The Iraqi elections seem to have posed almost as many dilemmas as they have resolved. The Sunni boycott leaves the former power-holders and a large part of the country effectively without political representation. The violence continues, allowing Iraq's neighbours and allies of all stripes to jockey for advantage amid instability on all sides.

Iran, accused - like Syria - of harbouring terrorists, is the recipient of barely disguised US threats over its nuclear programme. It, too, faces elections this year and has that perilous mix of a young population, potentially rebellious students, and an ageing clerical regime. Even relatively quiet Egypt may face difficulties over its own leadership succession before long. Amid such volatility, it would be all too easy for an event, such as yesterday's assassination, to light a fuse that would ignite conflicts far beyond Beirut. This is a time for cool heads and wise words, not hasty conclusions, least of all any rush to arms.