UNITED NATIONS/BEIRUT/JERUSALEM - Israel rejected proposals on Thursday for a ceasefire with Hezbollah, defying allies including the United States which had called for an immediate three-week halt in fighting to allow for diplomacy to avert a wider war.

"There will be no ceasefire in the north," Foreign Minister Israel Katz said on X. "We will continue to fight against the Hezbollah terrorist organization with all our strength until victory and the safe return of the residents of the north to their homes."

The comments dashed hopes for a swift settlement, after Prime Minister Najib Mikati had expressed hope that a ceasefire could be reached soon in Lebanon, where hundreds of thousands of people have fled their homes seeking safety.

World leaders voiced concern that the conflict - running in parallel to Israel's war in Gaza - was escalating rapidly.

The heaviest fighting in nearly two decades between Israel and the Iran-backed Hezbollah group has raised fears of a new Israeli ground offensive across the Lebanese-Israeli frontier.

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The United States, France and several allies called for the immediate 21-day ceasefire across the Israel-Lebanon border while also expressing support for a ceasefire in Gaza following intense discussions at the United Nations on Wednesday.

Israeli Prime Minister Benjamin Netanyahu, heading to New York to address the United Nations, said he had not yet given his response to the truce proposal but had instructed the army to fight on. Hardliners in his government said Israel should reject any truce and keep hitting Hezbollah.

Israeli airstrikes overnight hit around 75 Hezbollah targets in the Bekaa Valley and southern Lebanon, including weapons storage facilities and ready-to-fire launchers, the Israeli military said on Thursday.

In the latest deadly strike, at least 23 Syrians, most of them women and children, were killed when Israel hit a three-story building in the Lebanese town of Younine overnight, the town's mayor, Ali Qusas, told Reuters. Lebanon is home to around 1.5 million Syrians who fled civil war there.

The Israeli military said dozens of Hezbollah targets were attacked, including terrorists, military buildings and weapons depots, in several areas on Thursday morning.

Around 45 projectiles were fired from Lebanon towards the western Galilee area, some of which were intercepted with the rest falling on open ground, said the Israeli military.

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Israel widened its airstrikes in Lebanon on Wednesday and at least 72 people were killed, according to a Reuters compilation of Lebanese health ministry statements.

Netanyahu repeated pledges to ensure that tens of thousands of Israelis evacuated from northern border areas can return home. Finance Minister Bezalel Smotrich, who heads one of two nationalist-religious factions in Israel's governing coalition, said Hezbollah should be crushed and that only its surrender would make it possible for the evacuees to return.

Lebanon's leader Mikati welcomed the call for a truce but said the key to its implementation was whether Israel, which has been moving troops closer to Lebanon, is committed to enforcing international resolutions.

Asked if a ceasefire could be secured soon, Mikati told Reuters: "Hopefully, yes."

Mikati’s caretaker administration includes ministers chosen by Hezbollah, widely seen as the country’s most powerful political force.

The ceasefire would apply to the Israel-Lebanon "Blue Line," the demarcation line between the countries, and would allow the parties to negotiate towards a potential diplomatic resolution of the conflict, a senior Biden administration official said.

UN Special Coordinator for Lebanon Jeanine Hennis-Plasschaert on Thursday welcomed the call for an immediate 21-day ceasefire to allow the space for diplomacy to succeed.

Airstrikes pound Lebanon

Israel has made a priority of securing its northern border and allowing the return there of some 70,000 residents displaced by near-daily exchanges of fire, which Hezbollah initiated a year ago in solidarity with the Palestinian group Hamas in Gaza.

Israel's airstrikes sharply intensified since Monday, when more than 550 people were killed in Lebanon's deadliest day since the end of a 1975-1990 civil war.

Around half a million Lebanese have fled their homes and hospitals have been overwhelmed with the wounded. The bombing follows attacks last week when pagers and walkie talkies exploded across Lebanon, killing scores of people and wounding thousands.

READ MORE: Amid Israel-Hezbollah strikes, Lebanon says only US can stop fighting

Israel's military chief said a ground assault was possible, raising fears the conflict could spark a wider Middle East war.

Israel's UN Ambassador Danny Danon told reporters before a UN Security Council meeting on Wednesday that Israel would welcome a ceasefire and preferred a diplomatic solution. 

World leaders voiced concern that the conflict - running in parallel to Israel's war in Gaza - was escalating rapidly.

Israeli airstrikes this week have targeted Hezbollah leaders and hit hundreds of sites deep inside Lebanon. The group has responded with barrages of rockets fired into Israel.