BEIRUT (AP) — With all eyes on the Islamic State group’s onslaught in Iraq and Syria, a less conspicuous but potentially just as explosive front line with the extremists is emerging in Lebanon, where Lebanese soldiers and Shiite Hezbollah guerrillas are increasingly pulled into deadly fighting with the Sunni militants along the country’s border with Syria.

The U.S. has been speeding up delivery of small ammunition to shore up Lebanon’s army, but recent cross-border attacks and beheading of Lebanese soldiers by Islamic State fighters — and the defection of four others to the extremists — has sent shockwaves across this Mediterranean country, eliciting fear of a potential slide into the kind of militant, sectarian violence afflicting both Syria and Iraq, and increasingly prompting minorities to take up arms.