by Jason Ditz

While most of the factions within the Syrian Civil War are party to an ongoing ceasefire, neither ISIS nor al-Qaeda’s Nusra Front were invited to take part. As those two factions continue to clash with myriad other groups, they’re also finding time to fight against one another.

Heavy fighting erupted in the Syrian Qalamoun Mountains on Sunday, with ISIS pushing into regions held by al-Qaeda. The fighting raged into Monday, and moved further west, with both sides crossing into Lebanon, where al-Qaeda forces aimed to take ISIS territory along the border.

Lebanon has struggled with spill-over violence throughout the Syrian Civil War, with both ISIS and Nusra operating around the hills in the Bekaa Valley, and occasionally clashing with Lebanese security forces in the town of Arsal.

All told, at least 18 Nusra fighters were killed, along with 14 ISIS fighters. Six Nusra fighters were also reported captured in the battles. Though the fighting appears to have reached a lull by Monday evening, it is liable to pick up again at any moment.