US National Security Adviser John Bolton on Tuesday expressed “strong support” for Israel’s operation against Hezbollah attack tunnels crossing the Lebanese border, saying Washington backed Jerusalem’s “efforts to defend its sovereignty.”

In a tweet, Bolton called on the Iranian-backed Lebanese terror group to stop digging tunnels into Israel and refrain from responding to the operation.

He also called on Iran and “all of its agents” to cease “provocations” that threaten the Jewish state’s security.

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The Israel Defense Forces launched early Tuesday a large-scale operation to destroy cross-border attack tunnels constructed by the Shiite terrorist organization.

My statement in response to Hizballah’s tunneling across the Blue Line. pic.twitter.com/KbcutHUOpe — John Bolton (@AmbJohnBolton) December 4, 2018

Prime Minister Benjamin Netanyahu vowed to take additional steps, including clandestine operations, to protect Israel against Hezbollah’s efforts to attack the Jewish state.

“Anyone who tries to harm the State of Israel will pay a heavy price,” he said in a statement, his first public comment on the operation, dubbed Northern Shield.

Netanyahu, who also serves as defense minister and foreign minister, returned to Israel from Brussels early on Tuesday, after a snap meeting with US Secretary of State Mike Pompeo, during which the two discussed the operation.

The prime minister told the top US diplomat that the tunnels were “a flagrant violation of Israeli sovereignty and UN Security Council Resolution 1701,” according to a readout provided by Netanyahu’s office.

The Foreign Ministry in Jerusalem said Tuesday that Israel was not seeking war, and blamed the 2015 Iran nuclear deal for providing the Islamic Republic with cash that was used to help Hezbollah built its tunnels.

“Hezbollah is digging tunnels for terror purposes from Lebanon into Israel,” the ministry said in a statement, saying that those acts constituted “a severe attack on Israel’s sovereignty” and violated UN resolutions 1701, which ended the 2006 war with Hezbollah, and 1559, which called on Hezbollah to cease militant activity in 2004.

“Israel is conducting defensive actions within its sovereign territory. Israel has the right to defend itself and is not interested in escalation,” the ministry’s statement read.

Hezbollah has worked on “a broad expansion of its subterranean terror infrastructure” since the 2006 Lebanon War, the statement read, accusing the group of acting as Iran’s proxy.

“Hezbollah is building these terror tunnels in order to attack Israel, take Israeli citizens hostage and spread terror. Hezbollah’s tunnel project is another example of the dangerous strengthening of Hezbollah that is funded, supported and directed by Iran,” the Foreign Ministry said.

The Lebanese Armed Forces went on high alert in southern Lebanon after the IDF began the operation, a security official told the Lebanese al-Nahar news outlet.

A Lebanese military official told The Associated Press that Lebanese troops and military intelligence agents, along with UN peacekeepers deployed in southern Lebanon, were observing the border.

Al-Nahar quoted Hezbollah propaganda outfit War Media as saying that Lebanese border villages were not preparing for a wider outbreak of hostilities.

The army said the operation was taking place in Israeli territory, though spokesman Ronen Manelis, asked by Army Radio whether forces planned on crossing the border fence with Lebanon, said the campaign would expand in the coming days.

The IDF issued a stern warning to members of Hezbollah and the Lebanese army to stay away from any tunnels dug under the border and into Israel.

Israeli security chiefs were holding security assessments throughout the day in order to predict Iran-backed Hezbollah’s reaction to the operation.

Additional troops were deployed to northern Israel as a precaution against potential attacks by Hezbollah, but no reservists were called up.

Israel has long warned that Hezbollah planned to conduct cross-border raids in any future conflict, with the specific goal of attacking and conquering a civilian town near the border. Northern residents have raised fears in recent years of attack tunnels being dug under the border, spurring the IDF to launch a task force to investigate the concerns in 2014.

IDF spokesperson Jonathan Conricus said the tunnels “are not yet operationally ready” and therefore did not pose an “immediate threat.”

Raphael Ahren, Judah Ari Gross and agencies contributed to this report.