Some of the most intense fighting for weeks is raging in both the north and south of Gaza.
Israeli forces on Monday pushed deep into the ruins of Gaza's northern edge to recapture an area where they had claimed to have dismantled Hamas months ago.
In the south, tanks and troops pushed across a highway to Rafah, leaving Palestinian civilians, many of whom had fled to the city from other parts of the enclave, scrambling to find safety.
Settler attack on aid convoy 'utterly unacceptable': Sullivan
Israeli protesters blocked aid trucks headed for Gaza, strewing food packages on the road at Tarqumiyah checkpoint, west of Hebron in the Israeli-occupied West Bank.
The Israeli protest group Tzav 9 has claimed responsibility for the incident and other attacks on food convoys bound for Gaza.
The group says no aid should enter until all Israeli hostages are released by Hamas.
State Department deputy spokesman Vedant Patel said the US had raised concerns with officials in Israel.
"I will reiterate it here. It is our strong view that aid cannot and must not be interfered with," he said.
"We have raised this incident with the government of Israel and we expect them to take appropriate action."
Four protesters were taken into custody, according to local reports, citing Israeli police.
US national security adviser Jake Sullivan expressed concern about the attack, the second such incident in less than a week.
"It is a total outrage that there are people who are attacking and looting these conveys," Mr Sullivan said.
"It is completely and utterly unacceptable behaviour."
US Army major says he quit over support for Israel
The assault on Rafah has caused one of the biggest splits in decades between Israel and its main ally the US, which paused some deliveries of weapons.
As pressure builds on President Joe Biden during an election year, a former US military intelligence official released a letter on Monday explaining that his November resignation was due to "moral injury" stemming from US support for the Israel Defense Forces (IDF).
Harrison Mann explained to his colleagues at the Defense Intelligence Agency (DIA) that he left his position due to the harm caused to Palestinians.
The Army major would be the first known DIA official to quit over US support to Israel.
A US airman fatally set himself on fire in February outside Israel's embassy in Washington and other military personnel have protested.
Mr Mann said he kept quiet about his motives for resigning for months out of fear.
"I was afraid. Afraid of violating our professional norms. Afraid of disappointing officers I respect. Afraid you would feel betrayed. I'm sure some of you will feel that way reading this," he wrote in a letter shared with colleagues last month and published on his LinkedIn profile on Monday.
Rafah closed to aid as UN worker killed
Israeli operations in Rafah, which borders Egypt, have closed a main crossing point for aid.
Humanitarian groups say this has worsened an already dire situation.
Around half of Gaza's population took sanctuary there after Israel ordered evacuations from northern Gaza in October.
Gaza's health authority appealed for international pressure to reopen access via the southern border to allow in aid, medical supplies and fuel to power generators and ambulances.
"The wounded and sick suffer a slow death because there is no treatment and supplies and they cannot travel," it said.
A foreign UN security staff member was killed on Monday when a UN-marked vehicle travelling to a hospital in Rafah was struck — the first international UN fatality in the Gaza war, a UN spokesperson said, bringing the total death toll of UN personnel to about 190.
Fighting at refugee camp in Gaza's north
In northern Gaza's Jabalia, a sprawling refugee camp built for displaced Palestinians 75 years ago, Israeli forces pushed into an area where they claimed to have dismantled Hamas months ago.
Residents fled along rubble-strewn streets carrying bags of belongings. Tank shells landed in the centre of the camp and health officials said they had recovered 20 bodies from overnight air strikes.
"We don't know where to go. We have been displaced from one place to the next … We are running in the streets. I saw it with my own eyes. I saw the tank and the bulldozer. It is on that street," said one woman, who did not give her name.
An Israeli air strike on a house in Al-Nuseirat refugee camp in central Gaza Strip killed at least eight people, said Mahmoud Basal, a spokesperson of the Gaza Civil Emergency Service. He said several other people were wounded and missing.
The Palestinian death toll in the war has now surpassed 35,000, with 57 killed in the past 24 hours, according to Gaza health officials, whose figures do not differentiate between civilians and fighters.
Wiping out Hamas not 'likely or possible': US official
Israeli troops are seeking to wipe out Hamas. A senior US State Department official on Monday said Washington did not think that goal of total victory was "likely or possible".
The militant group, which has said it is committed to Israel's destruction, burst into Israel on October 7, killing 1,200 and taking more than 250 hostages, by Israeli tallies.
Hamas's armed wing said because of Israeli bombardments it had lost contact with militants guarding four Israeli hostages, including US-Israeli citizen Hersh Goldberg-Polin, who appeared in a video released by Hamas in late April.
Attending a Memorial Day ceremony on Monday to mark Israel's fallen soldiers, Prime Minister Benjamin Netanyahu said the war against Hamas was a struggle to secure Israel's "existence, liberty, security and prosperity".
"Our war of independence is not over yet," he said.
ABC/wires
