Hezbollah acknowledged "heavy" losses within its "leadership structure" and "military and material structure" during its ongoing conflict with Israel, in a statement issued Monday to mark the first anniversary of the Oct. 7 attack.

The group said it is "confident" in the "ability of our resistance to repel the aggression" in Lebanon in a message posted to one of its official Telegram channels.

One year of war, the group claimed, has shown Israel to be "a fragile entity that is unable to survive and continue without American support."

The U.S. and its allies "bear full responsibility for the killing, criminality, injustice and shocking human tragedies" experienced by the Palestinian and Lebanese people, the statement added.

-ABC News' Patrick Reevell and Morgan Winsor

The war in Lebanon continues to intensify as Israel marks the first anniversary of the Oct. 7 attack.

Beirut saw some of the heaviest Israeli airstrikes of the war so far overnight into Monday, with huge explosions again rising over the southern suburb and Hezbollah stronghold of Dahiya.

Strikes also continue in southern Lebanon, where the IDF said a third division -- the 91st Galilee Division -- joined the nascent incursion on Sunday.

Israel has intensified its bombing of Beirut since Thursday, launching dozens of attacks on Dahiya and its surroundings. New strikes land every few hours during the day, building to fierce nighttime barrages.

On Sunday night, a massive fiery blast lit up the sky over the capital after the IDF struck a weapons depot. Ammunition could be seen detonating following the attack.

Hezbollah, meanwhile, launched five rockets into the northern Israeli city of Haifa, injuring at least five people.

-ABC News' Patrick Reevell and Morgan Winsor

The Hostages and Missing Families Forum rallied outside Prime Minister Benjamin Netanyahu's Jerusalem residence on Monday morning to mark one year since hundreds were taken as hostages during Hamas' Oct. 7 attack in southern Israel.

Attendees sounded a two-minute siren outside Netanyahu's home, "urging him to end the abandonment of their loved ones and to bring back all the hostages in a deal -- the living for rehabilitation and the deceased for proper burial," the group wrote in a statement.

The Hostages and Missing Families Forum has been a part of massive public pressure on Netanyahu to reach a cease-fire and hostage-release deal with Hamas in Gaza.

There are around 101 hostages still being held by militants inside the strip, around two thirds of whom are thought to be alive.

-ABC News' Jordana Miller

Another division joined Israel's cross-border assaults into Lebanon on Sunday, Israel Defense Forces spokesperson Avichay Adraee said.

The 91st Galilee Division "began a limited and targeted ground operation in southern Lebanon," Adraee said in a post on X.

"Since the beginning of the war, the Galilee Division has been fighting defensively in tandem with numerous offensive operations targeting the enemy and its infrastructure in southern Lebanon from the air and on the ground," he said.

"Over the past few weeks, the division's forces have carried out hundreds of attacks and eliminated dozens of terrorists."