Israeli soldiers recaptured the crusader-era castle recently, giving the military a strategic toehold it once occupied for nearly two decades.

"The tunnel network was constructed within a civilian area at a location that provides operational control over the Galilee Panhandle region, only six kilometres from Metula (in Israel), and served as a central Hezbollah terrorist organisation hub in the area," the military said.

It said the tunnel network was funded by Iran and engineered to shelter hundreds of fighters.

"In one tunnel, approximately one kilometre in length, troops located six underground shafts, a storage room used for weapons, an anti-tank missile launcher, anti-tank missiles, grenades, ammunition, combat equipment, advanced medical equipment, and several living quarters, including shower facilities, restrooms, an operating room, and kitchens," the military said.

Footage released by the military showed one narrow tunnel -- similar to those found beneath Gaza -- equipped with washrooms, trunks full of clothes, beds, a folded wheelchair and other household items.

Beaufort castle's elevated position and location near the border with Israel has turned it once again into a desirable position as Israel pursues its ground invasion in Lebanon.

Israel overran the fortress during its 1982 invasion of Lebanon, after a prolonged battle with the Palestinian fighters hidden in the castle's maze of historic underground tunnels.

The castle was damaged by violent bombardment in the process.

Israel used it as one of its main observation posts until its troops withdrew in 2000, particularly for electronic listening.