In the impoverished Bab al-Tebbaneh and Jabal Mohsen neighbourhoods of Lebanon's second city Tripoli, the war in neighbouring Syria has aggravated decades-old sectarian and political tensions.
Regional and local powers have taken advantage of the situation, arming poor fighters in the neighbourhoods to fight a proxy war over Syria.
Jabal Mohsen, where most of the population belongs to President Bashar al-Assad's Alawite sect, has long backed the Damascus regime.
Majority-Sunni Bab el-Tebbaneh, however, supports the rebels who have been fighting to overthrow Assad for the past 31 months.
But sectarian fighting in the two districts started long before: since 2008, there have been 18 rounds of fighting, killing more than 200 and wounding 3,000 others.
The most recent clashes between the two, fought across the aptly-named Syria Street that divides them, started on October 21, killing 14 people.
After each round of violence, Lebanese troops deploy to the area, bringing a temporary calm to the streets of the city of 500,000 people, of whom 80 percent are Sunni and just 11 percent Alawite.
"We are suffering the consequences of the Syrian conflict," said Nabil Rahim, a Sunni cleric in the city who has long worked to soothe tensions between the two communities.
But Rahim sees three main factors fuelling violence in the city: the conflict in Syria, political tensions in Lebanon, and the country's own bitter sectarian problems that caused a civil war from 1975-1990.
"In Jabal Mohsen, we know that (powerful Lebanese Shiite movement) Hezbollah, Iran and the Syrian regime are providing weapons and funds," he says.
"It is more complicated in Bab al-Tebbaneh," he adds.
"Those doing the shooting are residents, Islamists and supporters of the March 14 coalition," one of Lebanon's main political groupings that has long opposed Assad.
"But many are fighting just for the money," he added.
Syria militarily and politically dominated its tiny neighbour for more than 30 years after Assad's father Hafez al-Assad intervened in Lebanon's civil war in 1976.
Its involvement, which waned when Assad withdrew his troops in 2005, polarised Lebanese politics. Today, the March 8 coalition supports Damascus' influence in Lebanon, and March 14 vociferously opposes it.
The violence raging in Tripoli now is in part the legacy of this intervention.
The war-scarred neighbourhoods saw their first clashes in 1976, when Alawites and supporters of Hafez al-Assad fought against the Palestinian Liberation Organisation then headquartered in Lebanon.
In the 1980s, the front changed to pit pro-Assad fighters against the Islamist Tawhid movement, which was strong in Bab al-Tebbaneh.
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Hundreds killed in massacre
Then in 1986, when Syrian troops entered Bab al-Tebbaneh, they and their Lebanese backers killed hundreds of people in a massacre remembered to this day.
Under the iron fist of the Syrian regime, there was a semblance of peace forced by control.
At that time, commerce and even mixed marriages between residents of Bab al-Tebbaneh and Jabal Mohsen flourished.
The assassination of former prime minister Rafiq Hariri in 2005 changed all that. Political tensions soared once again, and were further exacerbated by the outbreak of the Syrian conflict in March 2011.
Lebanon's most prominent Sunni politicians have denied ties to armed groups in the city, and have called for help to clear Tripoli of weapons.
Former prime minister and Sunni leader Saad Hariri has condemned the fighting as "a dirty war" waged by Assad against Tripoli through his "local tools", in reference to Jabal Mohsen's Alawites and pro-Assad movements.
Sunni leaders have also demanded the dissolution of the Jabal Mohsen-based Arab Democratic Party that represents Tripoli's Alawites, after two horrific car bomb explosions near two mosques in August killed 45 people.
The authorities have since issued arrest warrants for seven Alawites from Jabal Mohsen over the explosions.
The ADP, meanwhile, whose headquarters are in Jabal Mohsen, blames the violence on Sunni leaders.
Local journalist Ghassan Rifi says the fighting between the two neighbourhoods reflects regional strains over the Syrian conflict.
"The latest flare-up is the result of Syrian-Saudi tensions," Rifi told AFP, referring to Sunni-majority Saudi Arabia, a key backer of the anti-Assad revolt.
Rahim also says that some people in Tripoli's flashpoints are fighting for financial reasons.
"It's true that some fight to defend themselves, but others are driven by sectarianism and money".
One angry shopkeeper in the city was sure that the weapons and the money fuelling the cycle of violence was coming from outside.
"The gunmen in Bab al-Tebbaneh don't have the money to buy bread, how could they afford weapons?", he asked, accusing politicians of financing the fighters.
This week, as troops once again returned to the streets of Bab al-Tebbaneh and Jabal Mohsen, residents were sceptical that troops would bring lasting peace.
For Rahim, there can be no solution for Tripoli "until the Syrian crisis ends, there is national reconciliation, and all funding for weapons comes to a halt".