BEIRUT // Fighters from the Sunni Bab Al Tabbaneh neighbourhood in Tripoli are clear about who is to blame for the gun battles where their area meets the adjoining Alawite district.
"Hizbollah and Bashar Al Assad want this," said Sheikh Khodr Al Zoobi, a Salafist cleric, sometime school bus driver and militia leader. "There is a war against Sunnis in Lebanon."
With shots overhead from snipers in the Alawite neighbourhood of Jabal Mohsen, he argued that Hizbollah, a Lebanese Shiite militia and political party, had grown powerful at the expense of the Sunni community. "We need to stand our ground," he said last month.
Bab Al Tabbaneh, a poor neighbourhood of rundown apartment blocks dotted with the black flags of the conservative Islamic Salafist movement, is a microcosm of a wider issue in Lebanon and Syria.
The men exchanging fire with Sheikh Al Zoobi and his ragtag band of fighters are Alawites, a branch of Shia Islam. Over the border in Syria, this conflict is being played out on a wider and bloodier scale between the Alawite-dominated government of Mr Al Assad and the mainly Sunni rebels fighting to overthrow his regime.
As the Syrian civil war escalates, tensions between the two communities in Lebanon are rising and some Sunni groups - particularly in working-class districts of the cities of Sidon and Tripoli - are itching for a fight.
Lebanon's main Sunni political party, Future Movement, yesterday pleaded with the presidency to prevent "state collapse", blaming Hizbollah for dragging the country into the war in Syria.
Iranian-backed Hizbollah militants are openly fighting for Mr Al Assad, and sectarian violence has spread to religiously mixed Lebanese cities and border towns.
"Hizbollah is serving Syria and Iran at the expense of the Lebanese," said Fouad Siniora, the Future Movement leader and a former prime minister. He said the president, Michel Suleiman, should launch an initiative "to stop the state's collapse and give the Lebanese hope".
Recent incidents have hinted at growing anger among Sunnis. The clashes in Tripoli struck up again last month, were fiercer than ever. Rockets were fired into the Hizbollah-dominated Chiyah area of Beirut in late May, after the group's leader Hassan Nasrallah made an inflammatory speech in which he admitted that his men were fighting alongside government troops in Syria. And in the southern city of Sidon, gunmen shot at a pro-Hizbollah sheikh while Salafis blocked access to a Hizbollah funeral.
Randa Slim, an analyst at the Middle East Institute, said the incident at the funeral on May 22 was "very concerning".
"When it comes to funerals there is normally some respect for the dead in Islamic culture. This was a sign of the depth of the anger people feel about Hizbollah," she said.
Fighting broke out in Sidon again yesterday afternoon. Security officials said automatic rifles and rocket-propelled grenades were being used in the clashes between followers of a radical Sunni cleric, Sheikh Ahmad Al Assir, and unknown gunmen.
The rise of Hizbollah from a militia group to a political force to be reckoned with over the past decade has both galvanised Lebanon's Sunnis and increased tensions.
Sheikh Al Zoobi admitted that relations between Sunnis and Shiites in Lebanon were better before May 2008, when Hizbollah sent armed men into Sunni areas of Beirut to bend the government to its will in a spat over communications networks.
Across the political and economic spectrum, Sunnis speak of that as a watershed moment.
"After 2008, my family started talking about how Sunnis need to stick together and people became more wary of going into Shia areas," said Rania, a middle-class Sunni living in Beirut.
Now, the war in Syria has emboldened more militant Sunnis. Hizbollah has been fighting in Syria for some time, with its fighters playing a decisive role in the battle for Qusayr. They are now reported to be preparing an assault on Aleppo.
In his speech on May 25, Mr Nasrallah said that Hizbollah feared Sunni Islamists taking over in Syria and admitted that Lebanese Sunnis and Shiites have been fighting a proxy war over the border. "We disagree over Syria," he said, addressing the Sunni community. "You fight in Syria, we fight in Syria - then let's fight there."
In Sidon, the Salafist leader, Sheikh Al Assir, has formed what he calls the Free Resistance Brigade to wage war against the Syrian regime. He travelled there earlier this year, releasing photographs of him marching in Syria with a Kalashnikov in hand.
Sheikh Al Assir told his supporters in April that every able-bodied Muslim in Lebanon had a "religious duty to enter into Syria to defend its people, its mosques and religious shrines".
Fighters have also been joining the battle from the north of Lebanon, which has long been a base for Islamist Sunni groups and was the location of a three-month conflict between Salafis and the Lebanese army at the Nahr Al Bared Palestinian refugee camp in 2007.
There have been calls from the mosques there for men to go to Syria, including from the hardline cleric, Omar Bakri, who was deported from the UK and has based himself in Tripoli. He said about a third of the men who normally fight with him in Bab Al Tabbaneh had left to go to Qusayr.
Until now, this increased militancy has been largely limited to sections of disenfranchised working-class urban Sunni communities.
Yezid Sayigh, senior associate at the Carnegie Middle East Centre in Beirut, estimated that only 15 per cent of Lebanese Sunnis would consider themselves Salafis, and that the political class had shown little appetite for joining Syria's war.
"I don't see yet a will inside the Sunni community to fight Hizbollah," said Ms Slim, adding that "the Salafis who are trying to push that violent agenda are limited to Sidon and Tripoli - that may be why we haven't seen large-scale violence".
But she warned that Syrian war was a "wild card factor" and could tip Lebanon's fragile confessional peace over the edge.