The fragmentation of the Syrian state is rapidly spilling over the country’s borders. Lebanon, in particular, is facing the prospect of unprecedented state disintegration, and of the unravelling of its system of uneasy sectarian coexistence. This is by far Lebanon’s deepest crisis since the end of the 15-year civil war that ran from the mid-1970s to the late 1980s.

In Iraq, the Syrian spillover is being manifested primarily in almost-daily suicide bombs and car bombs that killed more than 1,000 people in September alone. But Iraqi domestic politics are not driven by events in Syria the way matters in Lebanon have been.

In the latest manifestation of the metastasis of the Syrian conflict into Lebanon, at least four people were killed in fighting between Sunni Muslim and Alawite militias last week in the northern city of Tripoli. This is merely the most recent of a series of violent incidents that have rocked the country, all linked to the conflict in Syria.

In August, two car bombs exploded at mosques in Tripoli, killing 42 people and wounding hundreds. A week earlier a bomb attack killed 20 in a Hizbollah-controlled area of southern Beirut. Rocket attacks, explosions and kidnappings have all been on the rise throughout the country.

The main Lebanese political forces have tacitly agreed, and barely managed, to more or less quarantine the direct spillover from Syria to the northernmost part of Lebanon. How long this can continue is increasingly questionable, given Hizbollah’s own direct intervention in Syria on the side of the Damascus dictatorship. This was a direct contravention of the 2012 “Baabda declaration”, in which all major Lebanese political factions agreed to stay out of regional conflicts.

But it was inevitable that the Syrian fighting would spread into northern Lebanon and that Hizbollah would feel compelled to support the Syrian regime, its partners and fellow Iranian client. As the stakes grow higher, the danger of the Syrian conflict extending itself into much or most of Lebanon – as it seems to have done in Iraq – intensifies.

In fact the Lebanese political crisis – fuelled, if not created, by the Syrian conflict – is perhaps even more alarming than the spillover of physical violence seen thus far. The Lebanese state is experiencing a degree of fragmentation and disarray that is, for its institutions, at least as severe as what happened in the worst periods of the civil war. The spillover thus threatening the equilibrium of unstable elements that has held Lebanon together, more or less, in recent years.

The Lebanese prime minister-designate, Tammam Salam, has been unable to form a cabinet since April, because of a bitter dispute between pro-and anti-Syrian factions, particularly Hizbollah.

An alliance of Sunni Muslim and Christian parties is pushing for a three-way division within the cabinet with Shiites, Sunnis and Christians each receiving eight seats. Hizbollah, however, is insisting on one extra seat for itself or its allies – in practice, demanding a veto over all major government decisions.

Hizbollah seeks total impunity in those parts of Lebanon in which it operates a de facto state-within-a-state, complete with its own foreign and defence policies and military, while at the same time aiming to block any decision it cannot accept involving the rest of the country. Its demand to be “first among equals” is not acceptable to the other factions. This impossible position is largely driven by the agendas of Hizbollah’s Syrian and Iranian patrons.

Hizbollah’s most immediate fears involve Lebanese government cooperation with and funding of the Special Tribunal for Lebanon, which has indicted five Hizbollah operatives for the 2005 assassination of former prime minister Rafik Hariri. He had reportedly been threatened by Syrian President Bashar Al Assad personally, shortly before his murder.

But there are far deeper problems lying beneath the Lebanese political surface. Most of the country’s governing and service-providing institutions – with the obvious exceptions of the cabinet itself, the internal security services and significant parts of the military – have been either systematically hollowed out or else taken over by Hizbollah. Those that have not been are under growing threat, as the paralysis over forming a new cabinet demonstrates.

The Lebanese are used to their country serving as a proxy battlefield for regional rivalries. But for many decades the state has not been so hollow, or the stakes for outsiders so high.

Lebanon finds itself trapped in concentric circles of alliances and rivalries. Internally and in neighbouring Syria there is the immediate conflict between pro-and anti-Al Assad forces. These groups are themselves proxies in larger regional rivalries pitting Iran against Saudi Arabia and its allies. And at the global level, there is a re-emerging conflict of interests between the United States and Russia that also filters down into the Lebanese context.

UN special envoy Terje Roed-Larsen was not exaggerating when he warned recently that “Lebanon today is facing the most dangerous situation in its history after the end of the civil war”.

The reality is that Syria is starting to look increasingly like Lebanon: fragmented, splintered and ruled in fact by different groups in their own discrete areas. The irony is that Syria’s transition into a Lebanese-like reality may destroy the ability of Lebanon to maintain its own uneasy equilibrium.

Hussein Ibish is a senior fellow at the American Task Force on Palestine, a columnist for Now Media and blogs at www.ibishblog.com

On Twitter: @ibishblog