BEIRUT // The tension between the two neighbourhoods of the northern Lebanese city of Tripoli, had been building for days - years, in fact.
On one side, Sunnis who are anti the Syrian regime and on the other, on the hill, are the Alawites, the same Shiite sect of Syrian president, Bashar Al Assad's, ruling elite and more allied with Lebanon's southern Shiite militia, Hizbollah.
The dividing line of this seaside city still bares the scars of former battles. And it was tense even before the rebellion in Syria broke out a year ago.
On Friday night, tempers exploded once more. By the time a shaky truce was reached on Saturday, two people were dead - one from each side - and 12 wounded, six of them soldiers trying to stop the killing.
The fighting underscored how the bloodshed in Syria is inflaming emotions in its tiny neighbour Lebanon.
The already deep divisions between Lebanese are being strained, and many fear the chaos in Syria, which has a history of military and political intervention in Lebanon, will bleed across the border.
Lebanon is split along sectarian lines, with 18 religions and sects. But it also has a fragile political faultline over the issue of Syria.
The two sides are the legacy of, and backlash against, Syria's virtual rule over Lebanon from its occupation from 1976 to 2005 and its continued influence, including a major backroom role in politics.
Tempers between them are high enough. But Syria opponents worry the regime may intentionally cause trouble during the crisis.
"The Syrian regime holds a lot of cards in Lebanon, and the biggest fear is that as the Al Assad regime gets more desperate, it would decide to use them to create regional chaos," anti-Syrian politician Mustafa Alloush said.
Among those cards is Hizbollah, the Syrian and Iranian-backed Shiite militant group with an arsenal of weapons more powerful than that of the Lebanese army.
Already, any talk about Syria is potential cause for a fight.
On a talk show on Al Jazeera this month, Lebanese writer and Syrian supporter Joseph Abu Fadel flew into a rage over taunts from the other guest, a Syrian opposition member. Mr Abu Fadel leapt from his chair and charged, fists clenched - and although the host got between them, Mr Abu Fadel managed to land a slap on his rival's face.
An earlier show on Lebanese television turned into a brawl when Mr Alloush called Syria's president a liar. His rival guest, Fayez Shukur, the head of the Lebanese branch of Syria's ruling party, hurled a glass of water in his face.
Northern Lebanon, in particular, is a powder keg. It is mainly Sunni and sympathetic to the Sunnis who form the backbone of the Syrian uprising. But it also has pockets of Alawites, the Shiite offshoot that makes up most of the Syrian regime's leadership and to which Mr Al Assad himself belongs. The Friday night clashes were between the mainly Sunni Bab Tabbaneh neighbourhood and the adjacent, Alawites-majority Jabal Mohsen.
Short bouts of gunfire or grenade attacks between them has been ongoing for years because of the sectarian tensions. But the violence has become more frequent.
Sunnis in Bab Tabbaneh resent their Alawites neighbours' backing of Mr Al Assad, while Jabal Mohsen residents accuse their rivals of giving aid to the uprising against him.
In Beirut last week, hundreds of Lebanese clashed outside the Russian Embassy after Russia and China vetoed a resolution at the UN Security Council to press Mr Al Assad to step down.
The tension comes at a time when anti-Syrian parties in Lebanon, who once ran the government, are weakened. They were replaced in 2010 by a government dominated by Hizbollah and pro-Syrian allies.
Prime Minister Najib Mikati says he isn't taking sides, adopting a policy of "disassociation".
Still, opponents accuse the government of complicity with Damascus. Lebanon voted against suspending Syria from the Arab League in November and was the only member state that did not endorse a League plan calling on Mr Al Assad to transfer powers to his vice president.
A long-time Syrian military presence in Lebanon ended after massive 2005 protests sparked by the killing of the former Lebanese prime minister, Rafik Hariri. Many Lebanese accuse Syria of involvement in the assassination, a charge Damascus denies.
A western-backed, anti-Syrian government was elected, but its stint in power was plagued by constant feuds with Hizbollah, until the Shiite movement succeeded in bringing it down and elevating Syrian nationalists to power.
Last week, media reported that legislator Sami Gemayel had been warned to take precautions because of a threat. Mr Alloushtakes the warnings seriously. "The Syrian regime is in trouble and as it goes down, the concern is that it will try to bring everyone down with it," he said.