A Lebanese security source said an Israeli strike killed four Hezbollah members in the country's south on Thursday, with the Iran-backed group announcing three dead fighters, as cross-border hostilities intensify.

Lebanon's powerful Hezbollah movement began attacking Israel in support of ally Hamas a day after the Palestinian militant group's unprecedented October 7 attack on Israel that sparked war in the Gaza Strip.

The Lebanese security source, requesting anonymity as they were not authorised to speak to the media, said that "four Hezbollah fighters were killed in an Israeli drone strike on their vehicle in Bafliyeh", about 15 kilometres (10 miles) from the frontier.

The Israeli army told AFP: "We do not comment on reports in the foreign media."

Lebanon's civil defence reported "four martyrs" in an "Israeli air strike" on the main road in Bafliyeh, adding that teams worked to put out the fire that broke out in the vehicle.

Hezbollah later said in separate statements that three of its fighters had been killed, and that it launched several attacks on Israeli military sites and troops across the border.

The Iran-backed Shiite Muslim movement has stepped up its attacks in recent weeks, while Israel's military has struck deeper into Lebanese territory.

At least 399 people have been killed in Lebanon in seven months of cross-border violence, mostly militants but also including more than 70 civilians, according to an AFP tally.

Israel says 14 soldiers and nine civilians have been killed on its side of the border. Three of the soldiers were killed this week, one of them on Wednesday.

Also on Wednesday, Hezbollah said two of its fighters had been killed, while Palestinian militant group Islamic Jihad said three of its own combatants died on the Lebanon-Israel border.

Tens of thousands of people have been displaced on both sides.