The head of Lebanon's Hezbollah warned of "war to the end" after the killing of a Hamas leader in Beirut.
Israel, which has laid waste to the Gaza Strip in an onslaught to wipe out its ruling Hamas group, has neither confirmed nor denied it assassinated Saleh al-Arouri in a drone strike in the Lebanese capital on Tuesday.
Arouri's killing was a further sign the nearly three-month-old Israel-Hamas war was spreading beyond Gaza, drawing in the Israeli-occupied West Bank, Hezbollah forces on the Lebanon-Israel border and even Red Sea shipping lanes.
In a televised speech in Beirut, Hezbollah leader Hassan Nasrallah said his powerful Iran-backed Shi'ite militia "cannot be silent" in the wake of Arouri's killing, which he called "a major dangerous crime", though he made no concrete threats of action against Israel.
Nasrallah said there would be "no ceilings" and "no rules" to Hezbollah's fighting if Israel launched full war on Lebanon.
"Whoever thinks of war with us, in one word, he will regret it. If war is launched against Lebanon, then Lebanon's national interests require that we take the war to the end."
Hezbollah, a Hamas ally, has been embroiled in nearly daily exchanges of shelling with Israel across Lebanon's southern border since the Gaza war began. More than 120 Hezbollah fighters and two dozen civilians have been killed on Lebanese territory, as well as at least nine Israeli soldiers in Israel.
Hezbollah and Israel last fought a major war in 2006 which ended in a stalemate. Analysts say Hezbollah has become a more formidable fighting force since with thousands of rockets, missiles and other heavy weaponry.
The U.N. peacekeeping mission in south Lebanon warned any escalation "could have devastating consequences for people on both sides of the border".
