JERUSALEM/CAIRO - Lebanon's Hezbollah militant group said on Friday it was moving to a new and escalating phase in its war against Israel while Iran said "the spirit of resistance will be strengthened" after the killing of Hamas leader Yahya Sinwar.

Sinwar, a mastermind of the Oct 7, 2023, attack that triggered the Gaza war, was killed during an operation by Israeli soldiers in the Palestinian enclave on Wednesday, a pivotal event in the year-long conflict.

Despite Western hopes of a ceasefire, Sinwar's death could dial up hostilities in the Middle East where the prospect of an even wider conflict has grown.

Israel has launched a ground campaign in Lebanon over the past month and is now planning a response to an Oct 1 missile attack carried out by Iran, ally of Hamas and Lebanon's Hezbollah.

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But the demise of the man who planned the attack last year in which fighters killed 1,200 people in Israel and captured more than 250 hostages, according to Israeli tallies, could also help push forward stalled efforts to end the war in which Israel has killed more than 42,000 Palestinians, according to Gaza health authorities.

US President Joe Biden, who spoke to Israeli Prime Minister Benjamin Netanyahu by phone to congratulate him, said Sinwar's death provided a chance for the conflict in Gaza to finally end and for Israeli hostages to be brought home.

The US wants to kick-start talks on a proposal to achieve a ceasefire and secure the release of hostages, US State Department spokesperson Matthew Miller said, calling Sinwar the "chief obstacle" to ending the war.

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Hezbollah was also defiant, announcing "the transition to a new and escalating phase in the confrontation with Israel".

US Secretary of State Antony Blinken held separate phone calls on Thursday with leaders in Saudi Arabia and Qatar aimed at ending the conflict in the Middle East, the State Department said.