People wave the flags of Lebanon and Iranian-backed Hezbollah at a rally last year in Beirut. (Nabil Mounzer/EPA)

A Saudi-dominated political bloc on Wednesday formally designated Lebanon’s Hezbollah militia a terrorist organization, a move that signals dangerously escalating tensions between regional rivals Saudi Arabia and Iran.

The Gulf Cooperation Council’s decision against the Iranian-allied group comes two weeks after Saudi Arabia canceled a $4 billion aid package intended to strengthen Lebanese security services.

The cancellation was rooted in anger over Hezbollah’s dominance of Lebanese security and political institutions. Saudi Arabia and other GCC member states quickly followed the scrapping of the aid package with advice to their citizens to leave Lebanon.

The growing rifts between Saudi Arabia and Iran have increasingly rattled Lebanon, where both nations until recently have managed to restrain their destructive rivalry despite their competing influence. Saudi Arabia and Iran also are on opposing sides in the civil war in neighboring Syria, where fighting has killed more than 250,000 people and displaced millions.

A blistering statement posted on the GCC website accused Hezbollah, a powerful Shiite Muslim movement, of “hostile acts” in the six states in the Sunni-led bloc: Saudi Arabia, the United Arab Emirates, Qatar, Bahrain, Kuwait and Oman.

The statement, citing GCC Secretary General Rashid al-Zayani, accused Hezbollah of recruitment to carry out terrorist attacks, and of smuggling weapons and explosives, “in flagrant violation of [GCC members’] sovereignty, security and stability.”

All Hezbollah leaders and the group’s affiliated factions fall under the new terrorism designation, said the statement, which also charged that the militia is responsible for “terror and incitement” in Yemen and Iraq.

There was no immediate response from Hezbollah.

Saudi Arabia and other allied nations broke ties with Shiite-led Iran in January. The rupture came after mobs stormed Saudi diplomatic missions in Iran in protest over Saudi Arabia’s execution of a prominent Shiite cleric accused of anti-state crimes.

Iran and Saudi Arabia for years have jostled for influence across the region.

Their rivalry has badly strained relations between Sunnis and Shiites the world over, and it has fueled devastating conflicts beyond Syria. In Yemen, a Saudi-led military coalition intervened with ground and air assaults last year against Iranian-aligned rebels.

Last week, Yemen’s Saudi-backed government accused Hezbollah of working in the war-torn Arabian Peninsula country to train the rebels, known as Houthis, who are followers of the Zaydi branch of Shiite Islam.

Wednesday’s announcement followed a provocative speech a day earlier by Hezbollah Secretary General Hassan Nasrallah, who criticized Saudi Arabia, its role in the region and its decision to halt military and security aid to Lebanon.

The decision to cut off aid, as well as other Saudi moves, signals that “we have entered a new phase of political and media struggle that Saudi Arabia has escalated,” Nasrallah said.

But the Hezbollah leader said there would not be a return to the kind of clashes that gripped Lebanon in 2008. That surge of unrest — pitting the group’s militants against Saudi-backed political forces in battles that locals described as a brief civil war — resulted in Hezbollah’s consolidating its unparalleled power in Lebanese affairs.

Divided by multiple, feuding religious groups, Lebanon fought a 15-year civil war that ended in 1990.

Militants from Iran and Hezbollah are fighting in Syria to prop up President Bashar al-Assad against a rebellion that is supported with money and weapons from Saudi Arabia and other states. Pro-Assad forces — backed by Russian air power — have made startling advances against rebels near the northern Syrian city of Aleppo, alarming Saudi Arabia, Turkey and other backers of the rebellion.

Some analysts speculate that the shift in momentum in Syria’s war compelled Saudi officials to press Iran by intensifying the pressure against it in Lebanon. Saudi Arabia also has suffered from falling oil prices, leading others to suspect that the decision to cut aid to Lebanon’s security forces was financially motivated.

Hezbollah intervened in Syria unilaterally, angering many Lebanese, who say that the move dragged Lebanon deeper into the conflict.

Despite the friction, Lebanon has managed to weather immense pressures.

More than 1 million Syrians have taken refugee in the tiny country of 4.4 million people. Gridlock in the government — partly a result of differences over the Syrian war — has prevented politicians from selecting a new president for nearly two years and has hampered garbage collection in Beirut.

But the recent surge in Saudi-Iranian tensions shows signs of spurring broader unrest.

Over the weekend, Hezbollah supporters staged demonstrations after a Saudi-owned pan-Arab satellite television station aired a comedy segment poking fun at Nasrallah. The show portrayed him as a stooge of Iran, sparking protests in which people blocked roads and burned tires.

Hezbollah has been pressured and denounced for decades by the United States and its allies over the group’s military opposition to Israel, including rocket barrages fired across Lebanon’s southern border. Hezbollah and Israel fought a brief but devastating war in 2006, but Israeli forces failed to dislodge the militants from bases in southern Lebanon.

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