The Israeli military has launched an operation meant to “expose and thwart” tunnels built by the Hezbollah militant group and stretching from Lebanon into northern Israel.

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.

Officers did not disclose how many tunnels snake into Israeli territory from Lebanon or how long the operation would last.

HezbollahIsraeli soldiers patrol at the village of Maroun el-Rass on the Lebanon-Israel border (AP)

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 US secretary of state Mike Pompeo.

Lt Col Jonathan Conricus, an Israeli military spokesman, said: “We see Hezbollah’s activities as a flagrant and blatant violation of Israeli sovereignty” and of UN resolutions.

“This activity is another example of the negative effects of Iranian entrenchment in the region.”

Israel has spent years attempting to tackle a network of tunnels from the Gaza Strip into Israel and has used a variety of methods to destroy tunnels and prevent them from being rebuilt.

Benjamin NetanyahuIsraeli prime minister Benjamin Netanyahu (AP)

A Lebanese military official said Lebanese troops and military intelligence agents, along with UN peacekeepers deployed in southern Lebanon, were observing the border on Tuesday.

Israel has been using bulldozers and other large machinery to build a massive wall along its northern border, saying the barrier is needed to protect civilians from Hezbollah attacks.

While the construction has prompted complaints from the Lebanese army, Hezbollah has not responded, an indication it could remain restrained amid the new operation.

Israel, meanwhile, gave no special orders to residents of northern Israel, signalling that it was not expecting an immediate response from Hezbollah.

GazaMr Netanyahu has promised to take a harder line in Gaza (AP)

The existence of the tunnels did not appear to have surprised Israel. Lt Col Conricus said Hezbollah has been developing an offensive plan against Israel that would “shift the battleground into Israel”.

The group would use firepower and ground units and “the surprise component of that plan was supposed to be tunnels that would allow infiltrators into Israel”.

He added that Israel has investigated the possibility of underground Hezbollah tunnels since 2013 and launched a task force which has been working for the last two years searching for them.

Israel has long voiced concern about Iran’s growing military presence along its northern border, warning of an Iranian corridor that could assist in the transfer of weapons to Hezbollah. Israel has generally refrained from engaging in Syria’s civil war, though it has carried out scores of air strikes against what Israel says were Iranian shipments of advanced weapons bound for Hezbollah.

The operation comes weeks after Mr Netanyahu faced a major crisis in his governing coalition over the handling of a ceasefire with Gaza militants.

Amid the crisis he took on the defence portfolio from his resigning minister and promised to pursue a hard line against Israel’s enemies during what he described as a “complex” security situation.