Gunmen have transformed Tripoli, Lebanon's northernmost city, into a war zone in the past week as rival groups fight duels using snipers and rocket-propelled grenades.

Syria Street is the front line – ironic given that it is the violence gripping its neighbour that has set these factions on their destructive path. And whether by design or chance, the war in Syria is seeping into Lebanon and vice versa.

Sheikh Bilal al-Masri, a street preacher with about a dozen armed followers, arrives in the alley behind his apartment and apologises profusely for making reporters climb through a hole beaten into a cinderblock wall behind the building. "I'm sorry we can't use the front door, but they know my face and are waiting to shoot me," he explains. "I put in the holes so I can move down to the street safely."

Masri is one of about a dozen militia commanders in Lebanon's poorest neighbourhood, Bab al-Tabbaneh, a slum populated by poor Sunni Muslims. It is notorious for crime under normal circumstances, but today it is at the heart of a sectarian war with its mostly Alawite neighbours in Jabal Mohsen.

With more than 17 people killed and scores wounded – many of whom are civilians – the political bosses in Tripoli have tried to put pressure on the combatants to continue with a ceasefire that was barely holding yesterday afternoon. "People need food, bread and water," Masri said. "But we are one bullet away from returning to the bunkers. This is only temporary, we're waiting to see if the army will go in to stop the snipers. If they don't by tonight, we'll do it ourselves."

Less than a minute later, a crack of gunfire echoes through the apartment building, which made Masri shake his head in frustration. "See, it's quiet, but if they see someone they know on the street, they try to get him," he said before continuing to explain what it will take to bring peace. "We need a new 'Lebanese' government instead of a bunch of Syrian criminals who lead us now," he said. "Until that happens, this will never stop."