METULA, Israel: Israel said on Tuesday it had launched an operation to "expose and thwart" cross-border attack tunnels from Lebanon dug by the Iran-backed movement Hezbollah and that their purpose was to send militants to attack Israel.
The Israeli military said its operations were currently confined to Israel and did not extend into Lebanon, where it said the tunnels originated.
The army released footage of tunnels and earth-moving equipment at work, carrying out what it said were "tactical preparations to expose Hezbollah's offensive cross-border tunnel project". Reuters could not immediately verify the footage.
The military said the tunnels were not yet operational, but posed "an imminent threat". Its Arabic media spokesman posted a message on Twitter warning the Lebanese army and Hezbollah to stay away, saying: "Your lives are in danger, you have been warned."
One tunnel originated under a house in the Lebanese border village of Kfar Kila and crossed the frontier near Israel's northernmost town, Metula, the Israeli military said.
There was no immediate comment from Hezbollah. The Lebanese army said the situation was calm on its side of the border, as did U.N. peacekeepers operating there. It said the military was "fully prepared to face any emergency".
Prime Minister Benjamin Netanyahu said late on Tuesday the tunnels were a grave violation of Israeli sovereignty.
"Hezbollah's intention was to insert terrorists into our territory through these tunnels," he said.
"These cross-border terror tunnels were built by Hezbollah with direct support and funding from Iran. They were built with one purpose in mind - to attack and murder innocent Israeli men, women and children."
Netanyahu, who on Monday met U.S. Secretary of State Mike Pompeo in Brussels to update him on the imminent operation, said it would continue for as long as necessary.
Throughout Tuesday mechanical diggers, drills and other heavy machinery could be seen from south Lebanon, working on the Israeli side of the heavily-guarded border.
Brigadier-General Ronen Manelis, Israel's chief military spokesman, described one video clip in which a man, who he said was a Hezbollah operative, was seen approaching a camera that Israel inserted into a tunnel. A small explosion scared him away and the tunnel was later blown up with a more powerful blast.
Mohammed al-Hadi, a school director in his 60s who has lived his entire life in Kfar Kila, said: "The current situation is not new for us. We are always living in a state of war and alert, worry and waiting."
Israel and Hezbollah have avoided major conflict across the Lebanese-Israeli border since their last war in 2006, though Israel has mounted attacks in Syria targeting what it said were advanced weapon deliveries to the Shi'ite Muslim group.
Israel's vulnerability to tunnels was laid bare during its war with Palestinian militant group Hamas in Gaza in 2014, when Palestinian militants used dozens of secret passages dug from Gaza into Israel to carry out ambushes.
In September, Netanyahu identified three locations in Lebanon where he said Hezbollah was converting "inaccurate projectiles" into precision-guided missiles - something Lebanon's government has denied.
(Reporting by Stephen Farrell, Ari Rabinovitch, Maayan Lubell and Ori Lewis in Jerusalem, Tom Perry and Lisa Barrington in Beirut; Editing by Mark Heinrich and Gareth Jones)