Israel's army chief has warned that its war with Hamas will last "many more months" as the military stepped up strikes inside the Gaza Strip, where more than 20,000 people have already been reported killed.

Concerns over a spiralling humanitarian crisis inside the besieged territory have amplified calls for an end to the hostilities, while incidents linked to Iran-backed groups acting in solidarity with Hamas have fanned fears of a wider regional conflict.

On Tuesday, the United States reported shooting down a barrage of drones and missiles over the Red Sea fired by Yemen's Houthi rebels.

But Israel's leaders have repeatedly vowed to keep up their offensive until Hamas is destroyed, and army chief Herzi Halevi signalled there would be no quick end to the war.

"This war's objectives are essential and not simple to achieve," Halevi said on Tuesday night. "Therefore, the war will continue for many more months."  

The war erupted when Hamas gunmen attacked Israel on October 7 and killed about 1,140 people, mostly civilians, according to an AFP tally based on Israeli figures.

During the attack -- the deadliest in Israel's history -- Hamas also took around 250 hostages, of whom 129 remain inside Gaza, Israel says.

Israel retaliated with a relentless bombardment and a siege followed by a ground invasion. The campaign has killed at least 20,915 people, mostly women and children, according to the latest toll issued by Gaza's Hamas-run health ministry.

'I've borrowed everything'

Since the siege went into effect, Gaza's 2.4 million people have been suffering severe shortages of water, food, fuel and medicine, with only limited aid entering the territory. An estimated 1.9 million Gazans have been displaced, according to the UN.

In the southern city of Rafah, where many displaced people have sought refuge, hundreds turned up at the Abdul Salam Yassin water company on Tuesday carrying baskets, pulling handcarts and even pushing a wheelchair stacked with bottles to queue for clean water.

"This was my father's cart," said Rafah resident Amir al-Zahhar. "He was martyred during the war. He used it to transport and sell fish, and now we are using it to transport fresh water."

Elsewhere in the city, people split logs and stacked kindling as the lack of fuel forced them to burn wood for cooking and to keep warm.

One woman took advantage of the sunshine on Tuesday to wash her family's clothes by hand, telling AFP: "I've pleaded with people for water. I have absolutely nothing. I've borrowed everything, even the blankets, from others."

The UN Security Council, in a resolution last week, called for the "safe and unhindered delivery of humanitarian assistance at scale".

'Gravely concerned'

Israeli army spokesman Daniel Hagari said Tuesday that troops were "fighting in the southern Gaza Strip in the area of Khan Yunis, and we have expanded the combat to the area known as the central camps".

Three more Israeli soldiers were killed in Gaza on Tuesday, bringing the total to 161 since its ground invasion began on October 27, the military said.

The UN Human Rights Office said it was "gravely concerned about the continued bombardment of Middle Gaza by Israeli forces", particularly after the military ordered residents to move to the central and southern regions.

Regional sparks

The impacts of the war have also reverberated throughout the region, with armed groups backed by Israel's arch-foe Iran escalating activity.

US military forces shot down more than a dozen attack drones and several missiles fired by Yemen's Iran-backed Houthi rebels at shipping in the Red Sea, the Pentagon said, reporting no damage or injuries.

The Houthis had claimed a missile strike on a vessel in the Red Sea and a drone attack towards Israel, their latest such actions in solidarity with Gaza.

Israel's military said one of its fighter jets had intercepted "in the Red Sea area a hostile aerial target that was on its way to Israeli territory".