Israel's military said on Tuesday it was beginning an operation to "expose and thwart" cross-border attack tunnels from Lebanon dug by the Lebanese militia Hezbollah.
A spokesman, Lt. Col. Jonathan Conricus, said the Israel military was aware of a number of tunnels crossing into Israel from Lebanon to the north, and that the army would only be operating within Israel and not crossing the border.
The military said in a statement it had "enhanced its presence and readiness in the Northern Command and is prepared for various scenarios".
Some areas near the border fence had been closed off.
"The digging of the cross-border attack tunnels that the IDF (Israel Defense Forces) has discovered before the attack tunnels became operational and posed an imminent threat to the safety of Israeli civilians, constitutes a flagrant and severe violation of Israeli sovereignty," the military said.
Israel and Iran-backed Hezbollah last fought a war in 2006.
(With inputs from agencies.)