Hundreds have been killed by Israeli attacks across Lebanon's ...

Hundreds of people are dead across Lebanon after the Israeli military carried out a bombing campaign in the country's south and east. 

Following what is said to have been Lebanon's deadliest day since its civil war, the US and UN have urged both parties to de-escalate tensions before war breaks out.

Here's what we know so far. 

After months of stewing tensions, Israel and the Lebanese militant group Hezbollah campaigns across the Israeli-Lebanese border has intensified, forcing thousands to flee.

The Israeli military bombed about 1,600 locations it said were Hezbollah targets throughout Lebanon on Monday, focusing on the country's southern border with Israel as well as the Bekaa Valley in Lebanon's east.  

Lebanese health authorities reported 492 people, including 35 children, were killed, and 1,645 were injured — many of them women and children.

Thousands of residents are fleeing southern Lebanon on packed roads and highways. (Reuters: Amr Abdallah Dalsh)

They said it was the deadliest day of violence since the country's 1975-1990 civil war.

Videos of the strikes show huge plumes of smoke rising from villages across the nation's south as buildings burn and are levelled by rocket fire. 

Israeli strikes hit Hezbollah sites hosting long-range cruise missiles, heavyweight rockets, short-range rockets and explosive drones, a spokesperson from the Israel Defense Forces (IDF) said.

Israeli warplanes have struck targets across southern Lebanon — traditionally a stronghold area for Hezbollah fighters and missile launchers, but also home to tens of thousands of civilians.

The Bekaa Valley, an agricultural area also known as a base for Hezbollah, has also been targeted in the IDF's aerial-bombing campaign, alongside several locations in the north and in the capital, Beirut.

More than 100,000 people in the south began evacuating in droves on Monday. Highways to the north were gridlocked and some people left their homes on foot, carrying their belongings.

Nasser Yassin, the Lebanese minister coordinating the crisis response, told Reuters 89 temporary shelters in schools and other facilities had been activated and they had capacity for more than 26,000 civilians fleeing "Israeli atrocities".

Abed Afou, who was evacuating with his family, said strikes were all around them, and described it as "terrifying". 

"I grabbed all the important papers and we got out," he said.

Israel has a long history of warring with Hezbollah, a militant group founded during a longstanding Israeli occupation of Lebanon. 

The group is designated as a terrorist organisation by the Australian government, but operates as a political party in Lebanon and has civilian services across the country.

Israeli Prime Minister Benjamin Netanyahu said the Israeli military's goal was to stop Hezbollah, not target the Lebanese people.

People carry belongings at a beach as they flee Tyre in southern Lebanon. (Reuters: Aziz Taher)

"Israel's war is not with you, it's with Hezbollah," he said.

"For too long Hezbollah has been using you as human shields."

The Israeli leader told Lebanese people living in the south to evacuate areas where Hezbollah was operating, warning of further strikes.

Israeli spokespeople including the defence minister have justified the strikes by claiming Hezbollah places weapons and infrastructure inside civilian houses. 

Hezbollah has rejected the claim. 

Hezbollah said it launched dozens of missiles at a military base in northern Israel in response to Monday's attacks, which came after days of heavy fire and bombardment across the Israeli-Lebanese border.

Sirens warning of Hezbollah rocket fire sounded across northern Israel, including in the port city of Haifa, and in the northern part of the occupied West Bank, the IDF said.

Hezbollah deputy secretary-general Naim Qassem said on Sunday the group had entered an "open-ended battle of reckoning" with Israel.

And last week, Hezbollah leader Hasran Nasrallah said Israel would receive a "just punishment" for allegedly orchestrating two days of attacks across Lebanon where thousands of hand-held pager and radio devices exploded after being booby-trapped with explosives. 

Israel has not claimed responsibility for those attacks, which killed 37 people and injured more than 3,000.

On Friday, an Israeli strike on a residential building in Beirut's south killed 37 people.

Among the dead were 16 members of Hezbollah, two of them senior commanders, the militant group confirmed.

About 60,000 people have been evacuated from northern Israel because of the cross-border fighting. 

Hezbollah, for its part, has vowed to fight until there is a ceasefire in Gaza, the Palestinian territory controlled by Hamas, with which it has strong links.

Though both sides have been urged to cease the daily missile and rocket fire, tensions between the Israeli government and Hezbollah leadership are still running high. 

Israeli Defence Minister Yoav Gallant said the IDF campaign would continue until those evacuated from northern Israel could return to their homes.

The UN, US and European leaders have all urged restraint from both sides, while Iran has accused Israel of provoking an all-out regional war.

A statement from G7 leaders Canada, France, Germany, Italy, Japan, the UK and the US warned the tit-for-tat strikes risked dragging the region into a broader conflict with "unimaginable consequences", and the group called for the cycle of violence to stop.

Iranian President Masoud Pezeshkian said Israel wanted to drag the Middle East into a full-blown war by provoking Iran to join the Israel-Hezbollah conflict.

"It is Israel that seeks to create this all-out conflict," he said.

A senior US State Department official said the US did not support a cross-border escalation between Israel and Hezbollah, and Washington was going to discuss "concrete ideas" with allies and partners to prevent the war from broadening.

ABC/Reuters