Israel has launched a heavy bombardment on southern Lebanon, forcing tens of thousands to flee and killing nearly 500 people on the deadliest day since the 2006 war with Hezbollah.

Israel issued warnings by text, radio and video to residents of southern Lebanon as it struck 1100 Hezbollah targets in civilian areas, claiming it was wiping out the militant group’s weapons.

Israel Prime Minister Benjamin Netanyahu urged families to “get out of harm’s way, now” as he set the stage for an intense Israeli offensive.

“For too long, Hezbollah has been using you as human shields,”  said Netanyahu in a video statement.

“It placed rockets in your living rooms and missiles in your garage.

“Those rockets and missiles are aimed directly at our cities, directly at our citizens.

“To defend our people against Hezbollah strikes, we must take out these weapons.”

Netanyahu said: “Once our operation is finished, you can come back safely to your homes.”

Lebanon’s health ministry said at least 492 people had been killed, including 35 children in Israel’s strikes on Monday (local time).

Defence Minister Yoav Gallant said the actions would continue until Israel achieved its goal of returning its residents to their homes in northern Israel.

Around 60,000 Israelis have been unable to live in northern Israel because of near-daily rockets fired from southern Lebanon.

After almost a year of Israel’s war against Hamas in the Gaza Strip on its southern border, Israel is shifting its focus to its northern frontier from where Hezbollah has been firing rockets into Israel in support of its ally Hamas.

Lebanon’s health minister Dr Firass Abiad said tens of thousands of people were fleeing their homes.

“We are in a new stage of war, initially it was targeted attacks but now it’s indiscriminate,” he told the BBC.

Israel’s military on Monday (local time) targeted Hezbollah in Lebanon’s south, eastern Bekaa valley and northern region near Syria in its most widespread strikes.

Netanyahu said Israel faced “complicated days” as it stepped up attacks against Hezbollah in southern Lebanon and called on Israelis to stay united as the campaign unfolded.

“I promised that we would change the security balance, the balance of power in the north – that is exactly what we are doing,” he said.

Israeli army spokesman Avichay Adraee earlier warned that air strikes were imminent on houses in Lebanon where “Hezbollah hid weapons”.

Reuters could not independently verify Israel’s allegation that Hezbollah had stored weapons in homes and villages.

In response, Israel’s arch foe Hezbollah said it had targeted a military base in northern Israel with dozens of missiles.

Another round of attacks was expected.

Israeli aircraft were preparing to attack Hezbollah strategic weapons stashed in houses in Lebanon’s Bekaa valley, the Israeli military spokesman said, calling on civilians to leave immediately.

“The sights now from south Lebanon are of secondary explosions of Hezbollah weapons, which are exploding inside houses. In every house we are attacking there are weapons. Rockets, missiles, unmanned aerial vehicles that were meant for and aimed at killing Israeli civilians,” Rear Admiral Daniel Hagari said in a televised statement.

Hezbollah has not commented on the Israeli claims it hid weapons in houses.

The air strikes have intensified pressure on Hezbollah, which last week suffered an attack its Secretary General Hassan Nasrallah called “unprecedented in the history” of the group, after thousands of pagers and walkie-talkies used by its members exploded.

The operation was widely blamed on Israel, which has not confirmed or denied responsibility.

In another major blow, an Israeli airstrike on Beirut’s southern suburb on Friday targeted senior Hezbollah commanders, killing 45 people, according to the Lebanese health ministry.

Hezbollah said 16 members of the group were among the dead, including senior leader Ibrahim Aqil and another commander, Ahmed Wahbi.

-with AAP