BEIRUT: Despite one of the quietest periods in decades along the Israel-Lebanon frontier, people on both sides of the border seem to fear that another eruption of violence is only a matter of time.

Sporadic flare-ups — like the exchange of fire on Friday — remind residents how easily fighting can be sparked. And an ongoing war of words between Israel and Lebanon's Shiite Hezbollah guerrillas has some convinced that one or the other of the two sides is planning a revival of the brutal war that they fought in the summer of 2006.

"This peace that you see today is not real. It is extremely fragile, it can blow up any minute, just as it did in 2006," said Salam Jalbout, a 45-year-old Lebanese Christian merchant who lives in the predominantly Shiite town of Khiam near the border.

Jalbout, whose house, shop and car were partially destroyed in the fighting three years ago, said the uncertainty was keeping badly needed investors and tourists away. "The situation is not reassuring at all," he said.

People south of the border in Israel are only slightly more optimistic.

"The residents are a little worried but they are brave heroes," said Jacky Sabag, mayor of the northern Israeli town of Nahariya, the target of Friday's rocket fire.

"We do not fear another war, and I hope there won't be one, but if there will be one then the city is ready and the residents are ready," said Sabag, whose town was hit by hundreds of Hezbollah rockets and emptied of most of its residents in 2006.

The 2006 war began when Hezbollah guerrillas attacked an Israeli border patrol, killing five Israeli soldiers and taking two of the bodies back into Lebanon. Israel retaliated with a massive bombardment and sent troops over the border, as Hezbollah fired rockets into northern Israel. The fighting killed around 1,200 Lebanese and 160 Israelis and devastated large parts of south Lebanon, the country's Shiite heartland.

But since the fighting was halted under a U.N. resolution, the border has enjoyed perhaps its most prolonged period of relative calm since the 1970s. Though Iranian- and Syrian-backed Hezbollah has boasted of rebuilding its arsenal of rockets, it has not fired across the border since the cease-fire. That has led to some to believe it is wary of sparking destructive Israeli retaliation that would undermine its support among the Lebanese — particularly now that it's playing a greater role in Lebanese politics.

The quiet has not been complete. Three times this year, Palestinian militants have fired rockets over the border into Israel, though they have caused no deaths. On Friday, two rockets were fired into northern Israel, prompting Israeli artillery fire against the launch area in southern Lebanon. There were no reports of casualties.

It is nothing like the violence during Israel's long occupation of southern Lebanon — or even during the years following Israel's 2000 withdrawal, when heavy exchanges continued to erupt. But it keeps residents on edge — as do persistent warnings from each side about the warlike intentions of the other.

In mid-July, a suspected Hezbollah arms depot exploded near the Israeli border, which Israel said was proof the group was rearming and stashing weapons in populated villages.

Israeli Prime Minister Benjamin Netanyahu warned the Lebanese government it would be responsible for any attack launched from its territory, and his defense minister, Ehud Barak, said Israel would "go after not only Hezbollah but the entire state of Lebanon."

Hezbollah leader Sheik Hassan Nasrallah, in turn, warned that his fighters would hit Tel Aviv if Israel attacks Beirut. Marking the third anniversary of the war this summer, Nasrallah said his men are now capable of striking any Israeli city — a boast that is largely supported by Israeli intelligence assessments.

Nasrallah has said that his group now has more than 30,000 rockets and has "surprises" in store.

Israel has also been preparing. In early September, a field intelligence unit known as Shahaf — Hebrew for "Seagull" — completed a large training maneuver with an eye toward war along the border, and other combat units have been regularly training for a guerrilla war in Lebanon's villages and thick underbrush.

Israel is also concerned Hezbollah could obtain anti-aircraft weapons, possibly Russian-made SA-18 shoulder-launched missiles, Israeli defense officials say.

Israel, whose aircraft currently enjoy unchallenged superiority over Lebanon and regularly violate Lebanese airspace with flyovers, has signaled unofficially to Lebanon and Syria that it will not accept the arrival of such weapons, the officials said, with the clear implication that this could lead to renewed fighting.

The officials spoke on condition of anonymity because they were not authorized to release that information to the media.

In Lebanon, Hezbollah expert Amal Saad-Ghorayeb said war at some point is probably inevitable.

Hezbollah has "re-imagined its strategy, arsenal and thinking to pose an even greater threat to its enemy to the south," she wrote in a recently published article entitled "The Hezbollah project: last war, next war."

"The movement has already set the strategic bar very high for itself for the next round of conflict," she wrote.

But Hezbollah might not want to hurt its political status in Lebanon by provoking Israel's wrath again, said Israeli analyst Yossi Alpher.

Israel's recent rhetoric directed at Lebanon has been aimed at making sure the Lebanese know they will all pay a price for any attack — and Hezbollah seems to have understood the message, Alpher said.

"There is really no indication that Hezbollah and Iran are planning something in the near future. But you never know," he said.