(AFP) - Israel launched air strikes into Lebanon on Sunday, saying that it had thwarted a large-scale Hezbollah attack, while the Lebanese group announced its own cross-border raids to avenge a top commander's killing.

The Israeli military said its fighter jets had destroyed "thousands" of Hezbollah rocket launchers "aimed toward northern Israel and some were aimed toward central Israel", far from the border.

Hezbollah, the powerful Iran-backed Lebanese armed group, countered that Israel was making "empty claims" of having thwarted a larger attack, and said its own operation for Sunday "was completed and accomplished".

The office of the United Nations special coordinator for Lebanon, Jeanine Hennis-Plasschaert, and the UNIFIL peacekeeping force urged "all to cease fire and refrain from further escalatory action".

Hezbollah said its leader Hassan Nasrallah was due to speak on the "latest developments" at 6:00 pm (1500 GMT).

The group has traded near-daily cross-border fire with Israeli forces throughout the Gaza war, in a campaign Hezbollah says is in support of Palestinian ally Hamas.

But fears of a wider regional conflagration soared after attacks in late July blamed on Israel killed Iran-aligned militant leaders, including Hezbollah commander Fuad Shukr, prompting vows of revenge.

Hezbollah, which last fought a major war against Israel in 2006, said its militants launched "a large number of drones" and "more than 320" Katyusha rockets targeting "enemy positions" across the border.

The Lebanese movement said its attack was an "initial response" to Shukr's killing, adding that it had "ended with total success", although the extent of the damage on the Israeli side was not immediately clear.

Lebanon's health ministry reported at least three dead in Israeli strikes in the country's south. No casualties were immediately reported in Israel.

- 'Larger attack' -

Israeli military spokesman Rear Admiral Daniel Hagari said his country's strikes were meant "to remove the threats aimed at the citizens of Israel".

Another military spokesman, Nadav Shoshani, said Hezbollah's strikes were "part of a larger attack that was planned and we were able to thwart a big part of it this morning".

Israeli authorities declared a 48-hour state of emergency but later relaxed most of the restrictions.

By 7:00 am (0400 GMT) flights had resumed at Israel's main international airport after a brief suspension, the aviation authority said.

In Lebanon, Beirut airport did not close but some airlines, including Royal Jordanian and Etihad Airways, cancelled flights.

Air France said it was suspending flights to Tel Aviv and Beirut for at least 24 hours.

The United States, Israel's top arms provider, said its military was "postured" to support its ally.

The Israel-Hamas war, triggered by Hamas's October 7 attack, had already drawn in Iran-backed groups like Hezbollah and Yemen's Huthi rebels.

The Huthis hailed the Hezbollah attack and declared that their own response for an Israeli strike on a key Yemeni port on July 20 was "definitely coming".

The fighting between Israeli forces and Hezbollah has killed hundreds, mostly in Lebanon, and displaced tens of thousands of residents in both southern Lebanon and northern Israel.

Some 605 people have been killed on the Lebanese side, mostly Hezbollah fighters, but including at least 131 civilians, according to an AFP tally.

On the Israeli side, including in the annexed Golan Heights, authorities say 23 soldiers and 26 civilians have been killed.

Israeli Prime Minister Benjamin Netanyahu convened his security cabinet and vowed "to do everything to... return the residents of the north safely to their homes" after more than 10 months of violence.

Lebanese Prime Minister Najib Mikati told an emergency cabinet meeting he was in contact with "Lebanon's friends to stop the escalation".

In a call with Israeli Defence Minister Yoav Gallant, his US counterpart Lloyd Austin reaffirmed "ironclad commitment to Israel's defence against any attacks by Iran and its regional partners and proxies", the Pentagon said.

- Gaza talks -

Shukr's death last month and an attack hours later that killed Hamas political leader Ismail Haniyeh in Tehran ratcheted up concerns that the Gaza war could spiral into a broader conflict.

Hamas said Hezbollah's Sunday attack was "strong", hailing it as "a slap in the face" for Israel.

In recent weeks, Western and Arab diplomats have sought to head off a broader response to the killings, as mediators were making their latest push towards a Gaza ceasefire and hostage release deal.

An official from Netanyahu's office said a decision would be made later about whether Israeli spy chiefs would attend planned talks in Cairo on Sunday.

Hamas has said a delegation would go to Cairo but only to meet Egyptian officials, rather than participate in the discussions.

On the ground in the besieged Palestinian territory, an AFP correspondent reported strikes and shelling in Gaza City, where rescuers said at least three people were killed.

Witnesses said battles raged in the area of Deir al-Balah, further south.

Hamas's October 7 attack on southern Israel resulted in the deaths of 1,199 people, most of them civilians, according to an AFP tally based on Israeli official figures.

Israel's retaliatory military campaign has killed at least 40,405 people in Gaza, according to the Hamas-run territory's health ministry, which does not break down civilian and militant deaths. The UN rights office says most of the dead are women and children.

Out of 251 hostages seized by Palestinian militants in their attack, 105 remain in Gaza including 34 the Israeli military says are dead.

© Agence France-Presse