Residents of Israel and Lebanon feared Wednesday that their countries were edging toward war after Israeli troops and the Lebanese Hezbollah militia exchanged deadly barrages across a fractious border earlier in the day.

The clashes, which began with a Hezbollah attack that killed two Israeli soldiers, marked one of the most serious flare-ups of violence in the area since a month-long war in 2006 and raised tensions in a volatile tri-border zone close to positions held by Syrian rebels, including Islamist factions. A U.N. peacekeeper was also killed, although it was unclear how he died.

Israeli Prime Minister Benjamin Netanyahu vowed that “whoever is behind today’s attack will pay the full price.” In addition to Hezbollah, Netanyahu said Israel would hold the governments of Lebanon and Syria — which Hezbollah is backing in its civil war— responsible for any attack originating from their territories. The Israeli leader, in the midst of a competitive election campaign, also blamed Iran, another ally of Hezbollah, for trying to open a new front against Israel. […]