Heavy fighting has erupted in northeastern Lebanon over the weekend between the major Islamist factions in the Syrian Civil War, ISIS and al-Qaeda’s Jabhat al-Nusra, who fought on the outskirts of the town of Arsal, which is housing tens of thousands of refugees.

Reports from the area suggest at least nine ISIS and seven Nusra fighters were killed in the weekend fighting, and local Sheikh Mustafa Hujeiri, seen as close to Nusra, is said to be trying to broker some sort of local truce between the two sides to end the fighting.

ISIS and al-Qaeda’s Nusra Front have years of acrimony fueling these fights, dating back to ISIS’ attempt to absorb Nusra and become the official al-Qaeda affiliate in Iraq and Syria, an attempt which led to ISIS’ ultimate split from al-Qaeda.

Since then, the two have fought over territory in Syria repeatedly, fighting which only really ended when their respective territories no longer had a common border. Even now, Nusra is said to be trying to establish mergers with other Islamist outlets to try to more directly compete with ISIS.

Both are keen to carry out strikes in Lebanon, and have a presence in Arsal, but this close proximity to one another seems to have boiled over into another round of fighting.