A huge fireball lit up the sky and plumes of smoke rose over south Beirut on Sunday as Israel unleashed intense air strikes targeting Hezbollah, nearly a year since the Gaza war erupted.

Officials said at least 23 were killed in the overnight strikes.

Lebanese Prime Minister Najib Mikati called on the international community to put pressure on Israel for a ceasefire as another strike hit the capital's southern suburbs.

Israeli forces were on high alert ahead of Monday's anniversary of Hamas's October 7 attack, which sparked the war.

After a devastating year-long conflict in Gaza, Israel has now turned its focus northwards to Hezbollah, Hamas's Iran-backed ally in Lebanon.

Lebanon's official National News Agency said Hezbollah's south Beirut stronghold was hit by more than 30 strikes. A petrol station and a medical supplies warehouse were hit.

"The strikes were like an earthquake," said shopkeeper Mehdi Zeiter.

Israel's military said it struck weapons storage facilities and infrastructure while taking measures "to mitigate the risk of harming civilians".

TV footage showed a massive fireball over a residential area, followed by a loud bang and secondary explosions. Smoke still billowed from the site after dawn.

In the Sabra area, near the southern suburbs, dozens of people, some carrying bags on foot and others on motorbikes, fled one of the most intense bombardments of the Israel-Hezbollah war.

Hezbollah said it targeted Israeli forces with artillery after they tried to infiltrate towards Khallat Shuaib in Blida, in southern Lebanon.

A statement said fighters fired rockets at Israeli troops during the evacuation of "dead and wounded soldiers" in the Menara border area after midnight.

Hezbollah also said it launched assault drones against an Israeli military base.

Ahead of Monday's grim anniversary, Israeli military spokesman Rear Admiral Daniel Hagari told a televised briefing: "We are prepared with increased forces in anticipation for this day", when there could be "attacks on the home front".

Last year's unprecedented October 7 attack on Israel by Palestinian militants resulted in the deaths of 1,205 people, mostly civilians, according to tallies based on Israeli official figures that include hostages killed in captivity.

One year later, Israel's war in Gaza against Hamas continues despite the focus shifting to Lebanon and Hezbollah.

On Sunday the military said it had encircled the Jabaliya area of northern Gaza after indications Hamas was rebuilding despite nearly a year of fighting.

The army said it had killed about 440 Hezbollah fighters in Lebanon "from the ground and from the air" since Monday, when troops began "targeted" ground operations against Hezbollah.

Israel says it aims to allow tens of thousands of Israelis displaced by almost a year of Hezbollah rocket fire into northern Israel to return home.

Israeli President Isaac Herzog called Iran an "ongoing threat" after Tehran, which backs armed groups across the Middle East, launched around 200 missiles at Israel Tuesday in revenge for Israeli killings of militant leaders including Hezbollah chief Hassan Nasrallah.

Iran's attack killed a Palestinian in the Israeli-occupied West Bank and damaged an Israeli air base, according to satellite images.

It came the same day Israeli ground forces began raids into Lebanon after days of intense strikes on Hezbollah strongholds. (AFP)