Israel’s military has launched an operation to find and destroy a network of Hizbollah “attack tunnels” running underground from southern Lebanon into northern Israel.

The Israeli Defence Forces (IDF) said Hizbollah, the Iranian-backed militant group, dug the tunnels over several years so its fighters could ambush Israeli soldiers and civilians.

The IDF would not say how many tunnels it had found but said that several had already crossed from Lebanese territory into Israel. None of the tunnels were operational yet and there was “no immediate threat” to Israel, the IDF said.

“Whoever tries to attack the State of Israel will pay a heavy price. We are taking determined and responsible action in all sectors simultaneously,” said Benjamin Netanyahu, the Israeli prime minister.

Hizbollah did not deny building the tunnels, saying in a statement that Israel was targeting tunnels "allegedly stretching from south Lebanon to settlements in northern occupied Palestine".