Lebanese Prime Minister Saad Hariri said his government would support Hezbollah if war broke out with Israel. (Dalati Nohra/Associated Press)

Lebanon's prime minister voiced concern Wednesday about "escalating" Israeli war threats, and said his government will support the Shia Muslim group Hezbollah if a new war breaks out with the Jewish state.

Saad Hariri's comments come amid heightened tensions in the Middle East following some of the sharpest exchanges in years between Israel and its Arab neighbours.

It also comes in the context of improved relations between Hariri's Western-backed coalition and the Iranian-backed Hezbollah since the two sides were forced to coexist in a fragile national unity government formed in November. The cabinet includes two ministers from the militant group, which fought Israel to a standstill in a month-long war in 2006 and clashed with supporters of Hariri in 2008.

"We hear a lot of Israeli threats day in and day out," Hariri said in an interview posted on the BBC's website. "Every day we have Israeli warplanes entering Lebanese airspace. This is something that is escalating, and this is something that is really dangerous."

Lebanon, which has a notoriously fractious political system, would unite if there were a fresh conflict with the Israelis, he said.

"I think they're betting that there might be some division in Lebanon, if there is a war against us," Hariri said. "There won't be a division in Lebanon. We will stand against Israel. We will stand with our own people."

'Hostage of Hezbollah'

Israel's foreign minister brushed aside the Lebanese leader's warning.

"As prime minister, he's simply a hostage of Hezbollah, which has veto power in his cabinet," Avigdor Lieberman told Israeli army radio.

Asked whether there might be a new war involving Lebanon and Syria, Lieberman said: "I very much hope not."

"We have no interest in heating up the fronts with any of our neighbours. At the same time, we won't be a punching bag. And we won't shrug off vitriol that's directed at Israel," he said.

Hariri's coalition narrowly defeated a Hezbollah-led coalition in parliamentary elections last year. However, Hariri was unable to form a government without Hezbollah and its allies, fearing a repeat of the violence seen in 2008, when Hezbollah militants swept through Sunni neighbourhoods of Beirut after the government moved to curb the group's military communications network.

Hariri said Hezbollah will be included in the government whether Israel likes it or not. Like previous governments, Hariri's government endorsed Hezbollah's right to keep its weapons and has been reluctant to take any strong action against the group for fear of sparking a crisis.

Lebanon's president warned Israel on Tuesday that a war against Lebanon would be "no picnic."

Last week, Syria's foreign minister accused Israel of "spreading an atmosphere of war" after Israeli Defence Minister Ehud Barak warned that the stalled peace process with Syria could result in an all-out regional conflict. Syria's Walid al-Moallem warned Israelis that "a war at this time will be transferred to your cities."

Lieberman said the Syrians "crossed a red line" and warned Syria its army would be defeated and its regime would collapse in a future conflict.