Updated

Israeli troops in the north were on alert Thursday over worries that the political turmoil in Lebanon might spill over into renewed violence on their shared border, following the collapse of the Lebanese government.

The Iranian-backed Hezbollah militant group and its allies threw the already volatile Lebanon into chaos on Wednesday by pulling out of the government and causing it to collapse.

Hezbollah, which clashed with Israel in a monthlong war in 2006, bolted over the government's continued cooperation with a U.N. tribunal investigating the 2005 assassination of former Lebanese Prime Minister Rafik Hariri.

Hezbollah expects the tribunal to indict some of its members. It timed the dissolution of the government to coincide with the White House visit of Lebanon's current prime minister, Hariri's son Saad.

A senior officer in Israel's northern command said commanders were following events in Lebanon very closely for any sign Hezbollah might try to heat up the already jittery northern border to deflect attention from the political turmoil.

Though troops have raised their level of alert, reserves have not been called up and no regular troops have been moved north from other areas, the officer said.

He spoke on condition of anonymity because he was not authorized to disclose military tactics.

Israeli Deputy Prime Minister Silvan Shalom on Thursday called the situation in Lebanon "very fragile." He said the government crisis is an internal Lebanese issue, but that Israel has "to be prepared for every scenario."

Retired general Yaakov Amidror told Army Radio the prevailing Israeli assessment is that Hezbollah has no interest at this point in a war with Israel. Both the militant group — and more important, Iran — prefer to keep Hezbollah primed to assault Israel in the event Iran is attacked, Amidror said.

In the current situation, Amidror said he would advise the military to "cast aside all these learned assessments from me and others" because the situation in Lebanon is so unsettled.

"Things are liable to slip out of the hands of decision-makers," he said. "You never know in such a volatile and delicate situation, where everyone has a lot of weapons, a lot of resentment, a lot of frustration — you never know where it could lead."

Israel's war with Hezbollah in 2006 was touched off by a Hezbollah border raid. Israel invaded Lebanon and Hezbollah retaliated with nearly 4,000 rockets fired into northern Israel in fighting that killed around 1,200 Lebanese and 160 Israelis, according to official counts from each side.

The Israel-Lebanon border has been largely quiet since. Hezbollah hasn't fired a rocket into Israel in the past four years — though Palestinian groups have — and the killing of an Israeli officer by Lebanese army fire in August was the military's first fatality on the frontier since 2006.

But although the U.N. truce that ended the fighting forbade Hezbollah to rearm, Israel believes the group has restocked its arsenal with even more powerful weapons.