Humanitarian workers already face a slew of challenges getting aid to civilians in the besieged Gaza Strip, and fear that as the Israel-Hamas war rages on they may be forced to halt operations.
"There are enormous needs" which are bound to grow, while there is "less and less access", said the head of a European charity, speaking to AFP.
Aid groups say the humanitarian crisis in the war-ravaged Palestinian territory, where the UN has warned of looming famine, has significantly deteriorated since Israeli troops entered eastern Rafah last week.
The Israeli military has launched what it called a "limited" operation, seizing on May 7 the Rafah crossing on the Egyptian border -- a key aid conduit that is now shut -- and sparking an exodus of Palestinians seeking safety further north in Gaza.
The latest fighting, more than seven months into the war, has cut off access to some areas and left aid crossings either closed or operating at a limited capacity.
A worker for the Paris-based non-governmental organisation Humanity & Inclusion (HI) in the Palestinian territories, also requesting anonymity, said: "We can't get our teams out, the security conditions are too unstable."
Israel has vowed to defeat remaining Hamas forces in the southern city of Rafah, which it says is the last bastion of the group whose October 7 attack triggered the war.
The attack on southern Israel resulted in the deaths of more than 1,170 people, mostly civilians, according to an AFP tally based on official Israeli figures.
Israel's campaign in Gaza has since killed at least 35,303 people, also mostly civilians, according to data provided by the health ministry in the Hamas-run territory.
Aid workers told AFP their organisations had regularly been denied access by Israeli authorities to certain areas or routes.
The Kerem Shalom crossing between Israel and southern Gaza has reopened following a brief closure, but humanitarian groups say Israeli tanks amassing there and repeated Hamas rocket fire have hindered operations.
A trickle of aid has entered via Kerem Shalom in recent days under "great risk, through an area of active hostilities", said a UN employee in Jerusalem.
Human Rights Watch charged this week that Israeli forces had repeatedly targeted known aid worker locations, even when their organisations had provided the coordinates to Israeli authorities to ensure their protection.
On Monday a UN employee was killed and another wounded when their vehicle was hit in Rafah.
Shaina Low, communications adviser for the Norwegian Refugee Council, said the organisation had subsequently "cancelled all of our movements for the rest of the day to mitigate risk to our staff".
The Israeli army said it was looking into the incident which occurred "in an area declared an active combat zone".
Since the war began, more than 250 humanitarian workers have been killed in Gaza, according to UN figures.
Aid workers complain of lengthy and convoluted procedures to coordinate their movements with the Israeli military via the United Nations and several Israeli agencies.
"We are seeing mishaps" even after COGAT, the Israeli defence ministry body overseeing civilian affairs in the occupied Palestinian territories, informs organisations they have clearance, said Tania Hary, head of Israeli rights group Gisha.
"It does point to something that's going wrong in the communication" between COGAT and the army, she said.
To avoid having to go through a series of mediators -- UN agencies, Israel's Coordination and Liaison Administration and then its parent agency COGAT -- some aid groups have opted for direct contact with Israeli military authorities.
But workers and officials told AFP this has mostly created further confusion.
Some also fear NGOs would accept conditions in direct communication with the military, which could set precedents other groups may not be willing to abide by.
The HI employee said: "Notifying them of our movements, which they're not supposed to hinder, is a way of reminding them of their accountability if anything goes wrong."
Humanitarian workers stress that Israel, as an occupying power, is required under international law to ensure aid reaches civilians in Gaza.
A military spokesperson said Thursday the army was in contact with international organisations "in real time" and ensuring "the best way possible to communicate as fast as possible".
Even if a full-scale invasion of Rafah is averted, humanitarian agencies say conditions are unsustainable.
Debris and destruction have rendered main routes and many other roads impassable, and a severe fuel shortage -- worsened since the Rafah crossing takeover -- has limited the use of vehicles.
"We're only going to places we can walk to," said the head of one aid group with about 50 workers in Gaza.
A Jerusalem-based humanitarian official, also speaking on condition of anonymity, said he recognised that "military imperatives" arise in conflicts and may limit aid operations.
But in the Gaza war, movement requests are denied too often and "we can hardly bring anything", he said.
"We can't work like this."
* The writer is from Agence France-Presse