The death toll from four days of fighting in the northern Lebanon city of Tripoli is now 42 dead and about 100 wounded.

Lebanese commandos, backed by helicopter gunships, claimed the capture of the Abdullah bin Masoud Mosque in the Bab al-Tabbaneh neighborhood on Monday. They said it was the headquarters of an Islamist commanders Shadi Mawlawi and Osama Mansour, linked to the faction Jabhat al-Nusra.

Troops fanned out through the surrounding area in search of gunmen, following the evacuation of civilians.

Security sources said 23 gunmen, 11 soldiers, and eight civilians have died since Friday night, when a military checkpoint was attacked.

Earlier Monday, assailants tossed a hand grenade at a police station in the Tripoli neighborhood of Mina.

The fighting is the worst spillover of the Syrian war since battles between the Lebanese army with fighters of the Islamic State and Jabhat al-Nusra Front in the border town of Arsal in August.

Jabhat al-Nusra has again said it will execute Ali Bazzal, one of the 27 Lebanese troops being held captive by it and the Islamic State after August’s fighting.

The execution was first threatened on Sunday morning if the Lebanese army did not halt operations in Tripoli, but the deadline was pushed back throughout the day.