BEIRUT, Lebanon — Islamist fighters from Syria killed 10 Lebanese soldiers and appeared to have captured more than a dozen others in an armed offensive that left them in a tense battle for control of a Lebanese border town, Lebanon’s army chief said Sunday.

The new toll was reported one day after fighters from Syria — who included members of rebel brigades, an affiliate of Al Qaeda and the extremist Islamic State in Iraq and Syria — carried out a series of attacks on army checkpoints that left them largely in control of the town of Arsal.

The two-day clash was the most recent spillover into Lebanon from the civil war in neighboring Syria. The two countries share a complex web of political and sectarian ties that have made the violence in Syria resonate in its smaller neighbor, where street clashes, car bombs and political deadlock related to the war in Syria have been common.

Residents, aid workers and Syrian rebels reached in Arsal on Sunday said that insurgents had seized the town but that it was surrounded by the Lebanese Army, which was shelling it.