Israel announced this week that its troops had started "ground raids" into parts of southern Lebanon, a stronghold of Hezbollah, after days of heavy bombardment of areas across the country where the group holds sway.

The bombing has killed more than 1,000 people, according to Lebanon's health ministry, and forced hundreds of thousands to flee their homes in a country already mired in economic and political crisis.

Israel, at war in Gaza since Hamas's October 7 attack, says it shifted its focus to secure its northern border and ensure the safe return of more than 60,000 people displaced by Hezbollah attacks over the past year.

On the Gaza front, the Israeli military said a strike three months ago killed three senior Hamas leaders, including Rahwi Mushtaha, the head of the militant movement's government in the war-ravaged Palestinian territory.

In Lebanon, the Israeli military said it hit "targets belonging to Hezbollah's intelligence headquarters in Beirut".

Lebanon's state-run National News Agency reported three air strikes on Beirut's southern suburbs, with a source close to Hezbollah telling AFP the target was an evacuated building that housed the group's media relations office.

Israel told Lebanese people to evacuate more than 20 villages and the city of Nabatiyeh.

"For your own safety, you must evacuate your homes immediately and head north of the Awali River. Save your lives," army spokesman Avichay Adraee said on X.

- Central Beirut strike -

Hezbollah said it fought off a bid by Israeli troops to advance at Fatima's Gate on the border.

It also said it set off two explosive devices against advancing Israeli forces as it kept up its cross-border rocket fire.

The military said an overnight strike killed 15 Hezbollah fighters in Bint Jbeil, an area heavily damaged during Israel's last war with the militant group in 2006.

Later the Lebanese army said one of its soldiers was killed when "the Israeli enemy targeted an army post in the Bint Jbeil area" -- the third death among its troops in the current escalation -- prompting retaliatory fire.

A Lebanese military official said it was the army's first response to Israeli fire since last October.

Israel earlier carried out a deadly air raid in downtown Beirut, hitting an emergency services facility run by Hezbollah, killing seven workers, the service said.

Hassan Ammar, 82, who had been staying in the high-rise building whose walls were partly blown out by the strike after he fled south Lebanon, said: "We are peaceful civilians in our homes."

Israel has yet to comment on the strike, but said it had hit about 200 Hezbollah targets "in Lebanese territory".

Lebanese Health Minister Firass Abiad said more than 40 paramedics and firefighters have been killed by Israeli fire in three days.

- Biden comments spook markets -

The latest strikes came after Hezbollah-backer Iran launched its second direct missile attack on Israel, prompting Prime Minister Benjamin Netanyahu to warn that Tehran would pay.

As Israel weighs retaliation for the Iranian missile strike, President Joe Biden said the United States was discussing possible Israeli strikes on Iranian oil facilities, in comments that sent oil prices spiking just a month before the US presidential election.

When asked by a reporter if he supported Israel striking Iran's oil facilities, Biden said: "We're discussing that."

Oil prices jumped five percent after he spoke.

Any sustained rise in pump prices could be hugely damaging for Biden's Vice President Kamala Harris as the Democrat confronts Republican former president Donald Trump in a November 5 election where the cost of living is a major issue.

Iran, which arms and funds Lebanon's Hezbollah, said it would step up its response if Israel counterattacked.

Israel's ground operations and strikes follow the killing in a massive bombing in south Beirut of Hezbollah's chief Hassan Nasrallah and other commanders.

Israel intercepted most of the 200 missiles launched by Iran. In the Israel-occupied West Bank, a Palestinian was killed by shrapnel.

Israeli Defence Minister Yoav Gallant warned that "those who attack the state of Israel, pay a heavy price".

Iran's Revolutionary Guards said its missiles were fired in retaliation for Nasrallah's killing alongside that of a general in the Guards' Quds force, as well as for the killing in July of Hamas leader Ismail Haniyeh in Tehran.

Lebanon's health ministry said 46 people were killed and 85 others injured by Israeli strikes over the previous 24 hours.

The Israeli military has said that eight of soldiers have been killed in combat in Lebanon.

- 'Sickening cycle' -

The impact of the war was also felt in Syria, where the Syrian Observatory for Human Rights monitor said an Israeli strike in Damascus killed four people, including Hassan Jaafar al-Qasir, Nasrallah's son-in-law.

Iranian media said a Revolutionary Guards military "adviser" in Syria, Majid Divani, succumbed Thursday to wounds sustained in an Israeli strike on Damascus earlier this week.

In Israel's commercial hub Tel Aviv, Liron Yori, 22, said he was worried about "where the war's going and I don't feel comfortable with it".

The fighting comes with many Israelis celebrating Rosh Hashanah, the Jewish new year, on Thursday.

Calls for restraint have multiplied but months of similar calls for Gaza failed to bring a ceasefire.

Hezbollah began strikes on Israeli troops a day after Hamas staged its October 7 attack on Israel, which resulted in the deaths of 1,205 people in Israel, mostly civilians, according to an AFP tally based on Israeli official figures that include hostages killed in captivity.

Israel's retaliatory offensive in Gaza has killed at least 41,788 people, the majority of them civilians, according to figures provided by the Hamas-run territory's health ministry. The UN has described the figures as reliable.

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