The military says the tunnels are not operational and that its work to expose them, which began on Tuesday, was taking place in Israeli territory.
The military did not disclose how many tunnels snake into Israeli territory from Lebanon or how long the operation would last.
Israel views the Iranian-backed Hezbollah and its vast weapons cache as a major threat. The two fought an inconclusive, month-long war in 2006.
The Israeli operation comes hours after Israeli Prime Minister Benjamin Netanyahu held a last- minute trip to Brussels to meet Secretary of State Mike Pompeo.
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