The Israel Defense Forces uncovered a fourth cross-border Hezbollah terror tunnel leading from southern Lebanon to Israel over the weekend.

The IDF warned that though the tunnel is now under Israeli control and that it no longer poses a threat to Israeli civilians, “whoever enters it from the Lebanese side forfeits his life.”

The tunnel joins a network of attack routes dug by the Iranian-backed Hezbollah terror organization, and its neutralization is part of the army’s ongoing “Operation Northern Shield.”

Israeli officials said the existence of the tunnels are a “serious violation of Resolution 1701 and the State of Israel’s sovereignty.” U.N. Resolution 1701 required all armed groups except the official Lebanese military to remain north of the Litani River following the end of the 2006 Second Lebanese War.

The IDF said it believes the tunnels were being prepared for future warfare, to enable terrorists to stream into Israel as part of a larger military effort, including above-ground invasions and rocket launches.

According to the army, the IDF is in the process of exposing additional tunnels. Two of them were found outside the town of Metula, near the Lebanese border.

Last week, Israeli Prime Minister Benjamin Netanyahu said Hezbollah would receive an “unimaginable” response if it attempted to stop the IDF from uncovering the tunnel networks.

“If Hezbollah makes the mistake, and decides, in any way, to attack us or to oppose our operation, they will be hit with unimaginable blows,” said Netanyahu. “Imagine what would happen if we did not do this. Imagine that on one gray foggy day Hezbollah would spring out of these tunnels and kidnap our people.”

Though all the operations are taking place inside sovereign Israeli territory, Israeli officials have said they would enter Lebanon, if necessary, to destroy the tunnels.

The recent operations have been in coordination with the U.N. Interim Force In Lebanon (UNIFIL) and Lebanese Armed Forces.