Recent clashes between Hezbollah and Syrian rebels on Lebanese soil have raised fears Lebanon is becoming a new front in Syria's civil war.

Many Lebanese blame this on Hezbollah, long the iron fist of both Syria and its ally Iran, and whose fighters have now become President Bashar Assad's shock troops, reportedly converging on Aleppo, Syria's bitterly disputed second city and commercial heart.

Last weekend, Hezbollah fighters fought Syrian rebels near the city of Baalbek in Lebanon's Bekaa Valley, Hezbollah's heartland.

Hezbollah units ambushed a column of Syrian rebels and their Lebanese Sunni allies infiltrating the border after the Free Syrian Army, the main rebel force, threatened to hit Hezbollah on its own turf for siding with the Syrian dictator.

The rebels Saturday fired 18 rockets and mortar rounds at Baalbek, the ancient Roman outpost that is the Bekaa's capital in reprisal for Hezbollah taking a leading role in a 3-week-old battle to capture the rebel-held strategic crossroads town of Qusair, 6 miles inside Syria.

No casualties were reported in the shelling, but the bombardment was an affront that Hezbollah could not ignore.

Sunday's fight was seen as the heaviest clash between the two sides in Lebanon itself since the Syrian war began in March 2011, and in the minds of many presaging worse to come.

Lebanese officials said more than a dozen Sunni rebels from the much-feared Jabhat al-Nusra, a jihadist organization linked to al-Qaida in Iraq, were killed, with only one Hezbollah fatality.

Not a major battle, but certain to intensify the hatred between the Shiite Hezbollah and the Sunni-led rebels, aggravating a 1,300-year-old religious schism between two Muslim sects that's becoming the leitmotif of the Syrian conflict, threatening to engulf the entire region in a religious war that began with the death of Prophet Mohammed in 632 A.D.

Lebanon has long been dominated by Syria in a quasi-occupation that began in 1976 and supposedly ended when Syria withdrew in the aftermath of the Feb. 14, 2005, assassination of Lebanese statesman and former Prime Minister Rafik Hariri.

The self-made billionaire, paramount leader of Lebanon's Sunnis, died because he had turned on the Damascus regime dominated by Assad's minority Alawite sect, an offshoot of Shi'ism.

The killing of Hariri in a massive suicide bombing in downtown Beirut was widely blamed on that regime although four Hezbollah members have since been indicted by a U.N.-mandated international tribunal.

Although Syria pulled back its troops from Lebanon, its powerful intelligence services maintained a strong presence and were widely seen as masterminding further assassinations of anti-Syrian figures.

Under Syrian protection, Hezbollah became more powerful than the Lebanese army or security services, and the weekend clashes serve to emphasize how a final showdown between the Party of God and its religious enemies in Lebanon, backed by Sunni powers like Saudi Arabia, seems to be increasingly inevitable.

On May 19, Hezbollah, backed by airstrikes and artillery fire, spearheaded an assault on Qusair, held by the Syrian Sunni rebels for a year.

Hezbollah took heavy casualties, mainly from elaborate rebel bomb ambushes -- a murderous irony since it was Hezbollah that pioneered such techniques fighting the Israeli occupation in south Lebanon from 1982 to 2000.

The Lebanese fighters, veterans of the campaign that drove Israel out of Lebanon, seized much of the town in fighting that still rages.

But the besieged rebels are holding out -- not a situation Hezbollah can allow to continue.

Control of the town in western Homs Province is vital to both sides. It sits astride supply lines linking Damascus with the Alawite heartland in northwestern Syria.

The Syrian rebels need it as a conduit for weapons and fighters from Lebanon.

But the wider objective is control of Homs province. If the regime holds that, it will be able to fend off the rebels and maintain a tenuous kind of legitimacy.

Meantime, Hezbollah, once hailed by the Lebanese for driving Israel from the area, is rapidly being blamed for dragging Lebanon, still not recovered from its 1975-90 civil war, into supporting a brutal regime that held Lebanon in thrall.

Critics have taken to calling the Party of God the Party of the Devil.

It sounds much more venomous in Arabic, but it indicates how Hezbollah, and its charismatic leader Hassan Nasrallah, have become outcasts.