UN peacekeepers in Lebanon warned on Saturday that the conflict between Israel and Hezbollah and Hamas militants was escalating with potentially dire consequences.

Israel has faced a fierce diplomatic backlash over incidents in south Lebanon that saw five Blue Helmets injured.

Lebanon's health ministry said Israeli air strikes on two villages near Beirut killed at least nine people. Official media later reported an Israeli strike targeted a market in Nabatiyeh, an important southern city.

Israel had earlier told residents of south Lebanon not to return home, as its troops fought Hezbollah militants in a war that has killed more than 1,200 people since September 23, and forced more than a million others to flee their homes, Lebanese authorities say.

"For your own protection, do not return to your homes until further notice... Do not go south; anyone who goes south may put his life at risk," Israeli military spokesman Avichay Adraee posted on X.

Hezbollah said it fired missiles into northern Israel, where air raid sirens sounded and the military said it had intercepted a projectile.

The Iran-backed militants have stepped up their attacks on targets in and around Israel's main northern city of Haifa.

Israel's military said Hezbollah fired about 320 projectiles into Israel over the weekend of Yom Kippur, which ended at nightfall.

It also said roughly 280 "terror targets" were attacked in Lebanon and Gaza over the same period.

For the third time, it declared a "closed military area" along the Lebanese border in northern Israel.

Such measures since late September have preceded ground operations inside Lebanon.

In an interview with AFP, Andrea Tenenti, spokesperson for the United Nations peacekeeping mission, UNIFIL, said he feared an Israeli escalation against Hezbollah could soon spiral out of control "into a regional conflict with catastrophic impact for everyone".

There was "no military solution", Tenenti said.

The UN mission said five peacekeepers have been injured during fighting in south Lebanon in two days, and Tenenti said "a lot of damage" had been caused to its posts there.

Around Israel, markets were closed and public transport halted as observant Jews fasted and prayed on Yom Kippur.

After the holiday, attention is likely to turn again to Israel's promised retaliation against Iran, which launched around 200 missiles at Israel on October 1.

Tehran said the barrage was retaliation for the killing of top militants and an Iranian general.

Israeli forces have been at war in Gaza since Hamas Palestinian militants on October 7 last year carried out the worst-ever attack on Israel.

Hezbollah, saying it was acting as a "support" front for Hamas, had been exchanging cross-border fire with Israel for almost a year.

But on September 30 Israel began a ground offensive against Hezbollah in Lebanon after intensifying air strikes on targets there.

On Friday, Israel faced criticism from the UN, its Western allies and others over what it said was a "hit" on a UN peacekeeping position in Lebanon.

Two Sri Lankan Blue Helmets were hurt in the second such incident in two days, UNIFIL said on Friday.

Israel's military said soldiers had responded to "an immediate threat" around 50 metres (yards) from the UNIFIL base in Naqura, and pledged to carry out a "thorough review".

The Irish military's chief of staff, Sean Clancy, said it was "not an accidental act", and French President Emmanuel Macron said he believed the peacekeepers had been "deliberately targeted".

Both countries are troop contributors to UNIFIL. (AFP)