Trucks carrying desperately needed aid began moving into the besieged Gaza Strip on Saturday as Foreign Secretary James Cleverly warned that the delivery must not be a "one off".
Just 20 trucks were allowed through the Rafah border crossing from Egypt, an amount that aid workers said isn't enough to tackle the humanitarian crisis in Gaza.
Water and medical supplies including trauma medicine were among items delivered to hospitals and aid agencies in the besieged enclave.
Speaking at the Cairo Peace Summit, Mr Cleverly said the aid flowing through the Rafah crossing into Gaza was a “lifeline" but he said that access had to be maintained to provide humanitarian relief.
“Trucks carrying lifesaving aid are beginning to cross at Rafah into Gaza," he said.
“But it cannot be a one-off. The UK continues to push for humanitarian access to Gaza.”
He urged countries to work together to avoid a regional war.
"We must work together to prevent the tragic situation in Gaza becoming a regional conflict because that is exactly what Hamas wants," he told Western leaders.
More than 200 trucks carrying roughly 3,000 tons of aid have been positioned near the Rafah crossing for days.
Gaza's 2.3 million Palestinians, half of whom have fled their homes, are rationing food and drinking dirty water. Hospitals say they are running low on medical supplies and fuel for emergency generators amid a territory-wide power blackout.
Israel is still launching waves of airstrikes across Gaza that have destroyed entire neighbourhoods, as Palestinian militants fire rocket barrages into Israel.
Israel's military spokesman, Rear Admiral Daniel Hagari, said the country planned to step up its air strikes starting Saturday as preparation for the next stage of the war.
"We will deepen our attacks to minimise the dangers to our forces in the next stages of the war. We are going to increase the attacks, from today," Mr Hagari said, repeating his call for Gaza City residents to head south for their safety.
The border opening came after more than a week of high-level diplomacy by various mediators, including visits to the region by US President Joe Biden and UN secretary-general Antonio Guterres.
Israel had insisted that nothing would enter Gaza until Hamas released all of the captives from its attack, and the Palestinian side of the crossing had been shut down by Israeli airstrikes.
Late on Friday, Israel said Hamas freed two American hostages who had been held in Gaza since the war began, but it's unclear if their release is linked to the aid deliveries.
"This first, limited water will save lives, but the needs are immediate and immense," said Unicef executive director Catherine Russell.
The World Health Organisation said four of the 20 trucks that crossed through Rafah were carrying medical supplies, including essential supplies for 300,000 people for three months, trauma medicine and supplies for 1,200 people, and 235 portable trauma bags for first responders.
"The situation is catastrophic in Gaza," said the head of the UN's World Food Programme, Cindy McCain.
"We need many, many, many more trucks and a continual flow of aid."
She added that some 400 trucks were entering Gaza daily before the war.
The Hamas-run government in Gaza also said the limited convoy "will not be able to change the humanitarian catastrophe", calling for a secure corridor operating around the clock.
Rear Admiral Daniel Hagari, an Israeli military spokesman, said "the humanitarian situation in Gaza is under control".
He said the aid would be delivered only to southern Gaza, where the army has ordered people to relocate, adding that no fuel would enter the territory.
US secretary of state Antony Blinken appealed to all sides to keep the crossing open for crucial aid shipments and warned Hamas to not take the aid.
"Palestinian civilians are not responsible for Hamas's horrific terrorism, and they should not be made to suffer for its depraved acts," he said in a statement.
"As President Biden stated, if Hamas steals or diverts this assistance it will have demonstrated once again that it has no regard for the welfare of the Palestinian people."
Meanwhile Israel traded fire along its northern border with Lebanon's Hezbollah militant group, raising concerns about a second front opening up.
The Israeli military said on Saturday it struck Hezbollah targets in Lebanon in response to recent rocket launches and attacks with anti-tank missiles.
The Hamas-run Gaza Health Ministry said on Saturday that the death toll has reached 4,385, while 13,561 people have been wounded.
More than 1,400 people in Israel have been killed, mostly in the initial attack on October 7. In addition, 203 people were believed captured by Hamas during the incursion and taken into Gaza, the Israeli military has said.
