Defence Secretary Grant Shapps said Monday that Britain is "willing to take direct action" against Iran-backed Huthi rebels in Yemen who have repeatedly attacked vessels in the Red Sea.

London's warning comes amid escalating tensions in the vital shipping lane, with US Navy helicopters firing Sunday on Huthi rebels who attempted to board a cargo ship.

The rebels, who seized Yemen's capital Sanaa in 2014 and control much of country including its Red Sea coastline, have reported 10 fighters dead or missing.

The Huthis -- who say they are acting in solidarity with Palestinians in the Israel-Hamas war in Gaza -- have repeatedly fired drones and missiles at passing ships in the seaway through which 12 percent of global trade passes.

Hours after the latest incident, Shapps said Britain could step up its own military interventions. A British destroyer shot down a suspected Huthi attack drone in the Red Sea in mid-December.

"We are willing to take direct action, and we won't hesitate to take further action to deter threats to freedom of navigation in the Red Sea," he wrote in the Daily Telegraph newspaper.

The Huthis "should be under no misunderstanding: we are committed to holding malign actors accountable for unlawful seizures and attacks".

Shapps described the situation in the region as "a test for the international community" which had implications for other potentially contested waterways around the world.

"If we do not protect the Red Sea, it risks emboldening those looking to threaten elsewhere including in the South China Sea and Crimea," he added.

"We need to stand firm with our allies, stand firm for our beliefs and stand firm for innocent people caught up in these events."

The Telegraph said London is drawing up plans with Washington for potential military strikes against the Huthis, and reported that a joint statement giving the rebels a final warning to stop their attacks was imminent.

British Foreign Secretary David Cameron said Sunday he had spoken to his Iranian counterpart  Foreign Minister Hossein Amir-Abdollahian about the Red Sea tensions.

"I made clear that Iran shares responsibility for preventing these attacks," he said on social media, noting Tehran's "long-standing support" for the Huthis.

Israel warns Gaza war will continue throughout 2024

Israel warned its war against Hamas will continue throughout 2024 as unrelenting strikes killed two dozen people in Gaza and the Palestinian militant group fired a rocket barrage at the stroke of midnight.

Israeli military spokesman Daniel Hagari said in a New Year's message that some of the 300,000 army reservists would get a break from the war, in order to prepare for the "prolonged fighting" ahead.

The army "must plan ahead, understanding that we will be required for additional tasks and warfare throughout this year," Hagari said as the conflict sparked by the October 7 Hamas attacks raged on.

Heavy artillery fire again pounded targets in Hamas-run Gaza, killing at least 24 people, health ministry officials there said, with attacks reported across the length of the territory.

In the besieged Gaza Strip, where the UN says 85 percent of the population has been displaced, 20-year-old Hamdan Abu Arab said he hoped "2024 will be better".

"We used to go out and enjoy our time on the last day of the year," he recalled. "But this New Year's Eve, there are only missiles and the remains of people."

Hamas marked the start of the year by firing a rocket barrage at Israel in what it called a "response to the massacres of civilians".

AFP journalists in Tel Aviv witnessed missile defence systems intercept rockets overhead as some revellers ran for cover and others kept up the party with a shrug.

"My heart was pounding," said one, Gabriel Zemelman, 26, shortly after the rocket fire. "It's terrifying. You just saw the life we live, it's crazy."

The bloodiest ever Gaza war was triggered by Hamas's October 7 attacks on Israel, which resulted in the deaths of around 1,140 people, most of them civilians, according to an AFP tally based on official figures.

The militants also took around 250 people hostage that day, more than half of whom remain in Gaza, according to Israeli officials.

Israel has vowed to destroy Hamas and launched a punishing offensive that has reduced vast areas of Gaza to a ruined wasteland and killed at least 21,822 people, mostly women and children, according to the territory's health ministry.

The Israeli army says 172 of its soldiers have been killed inside Gaza in the battle against the Islamist militant group which Israel, the United States and European Union have designated a "terrorist" organisation.

- 'We live like animals' -

Prime Minister Benjamin Netanyahu warned on Saturday that the fighting would last "many months until Hamas is eliminated and the hostages are returned".

Hagari said "we are also currently adapting the planning of the force deployment in Gaza and the reserve system. Some of the reservists will return to their families and employment this week.

"This will significantly ease the burden on the economy and allow them to gather strength for the upcoming activities in the next year, as the fighting will continue and they will still be required."

Since Israel imposed a siege at the outset of the war, Gazans have been facing dire shortages of food, water, fuel and medicine.

UN chief Antonio Guterres has condemned the "epic human suffering" and "collective punishment" of Palestinian civilians, while the WHO has warned of the risk of hunger and infectious disease.

"We are exhausted... We were displaced five times during this war," said 29-year-old Bassam Hana.

"We hope things improve in 2024 and that we live just like any other human being. Currently, we live like animals."

At least 48 Palestinians were killed in strikes on Gaza City over the weekend, the territory's health ministry said, with many still buried under the rubble.

"After the explosion we arrived at the scene of the strike and saw martyrs everywhere," said one resident after a building was hit. "Children are still missing, we can't find them."

Hagari, in a briefing on Sunday, said several militants "were killed and subdued during the battles in Khan Yunis", the main southern city, earlier in the day.

"We are continuing to handle the underground tunnels and to strike the rocket launching array, in order to reduce rocket fire into the State of Israel," he said, adding that "dozens of aircrafts are in the skies of Gaza at any given moment".

- Regional fears -

International mediators have continued efforts toward a new pause in fighting.

A Hamas delegation from Qatar visited Cairo on Friday to discuss an Egyptian three-phase plan proposing renewable ceasefires, a staggered release of hostages for Palestinian prisoners, and ultimately an end to the war, sources close to Hamas said.

Their allies Islamic Jihad said on Saturday that Palestinian factions were evaluating the proposal and would give a response "within days".

The war in Gaza has raised fears of a broader regional conflict, with hostilities flaring with mostly Iran-backed militant groups in nearby countries who say they are acting in support of Hamas.

The Israeli army announced Sunday night having intercepted two "hostile aircraft" launched from Syria towards northern Israel.

Earlier it had reported launches toward Israeli territory from Lebanon, where it has fought the Hezbollah militant group.

"Throughout the day, IDF (military) tanks and helicopters targeted three terrorist squads operating in Lebanon," the army said in a statement.

And in the Red Sea, the US military said Sunday that Navy helicopters had fired at Iran-backed Huthi rebel boats off Yemen that were attacking a cargo ship, with Yemeni sources reporting 10 rebels killed.