Israel begins operation to 'expose and thwart' Hezbollah tunnels

In a statement, the army said it has implemented a "unique defensive plan" along the northern border, including the construction of a defensive wall, creating cliffs and clearing vegetation. A dedicated team has been working on thwarting Hezbollah tunnels since 2014, the statement said.

The Israeli army called the tunnels a "flagrant and severe violation of Israeli sovereignty," in the statement. Israel and Hezbollah -- the Iranian-funded militant group and political party -- were last engaged in a war in 2006, and have frequently exchanged threats since then.

Hezbollah has declined a CNN request for comment. Hezbollah-owned Al Manar TV proceeded with regular programming, even airing a report about traffic problems in Lebanon while news of Israel's operation broke.

A spokesman for the Israeli Foreign Ministry said the operations were taking place inside Israeli sovereign territory.

Residents in northern Israel have been told they do not need to take precautions, but can get on with their daily lives. A number of areas adjacent to the northern Israel security fence have been declared "closed military zones."

The United Nations peacekeeping mission in south Lebanon, UNIFIL, told CNN it was "aware of the reports."

"UNIFIL is liaising with all relevant interlocutors to ensure that the parties use the UNIFIL liaison and coordination mechanisms to maintain the continued calm and stability. The situation in UNIFIL's area of operation remains calm," said UNIFIL spokesperson Malene Jensen.