The UN children's agency on Thursday said that one of its vehicles was "hit by live ammunition" while waiting to enter the northern Gaza Strip on Wednesday.
"The incident has been raised with relevant Israeli authorities," UNICEF said in a statement but did not mention who opened fire on its vehicle.
"Sadly, humanitarians continue to face risks in delivering lifesaving aid," it added.
It also stressed that "unless humanitarian aid workers are protected, in accordance with IHL (International Humanitarian Law), humanitarian aid cannot reach people in need."
In March, the UN warned that northern Gaza could be hit by famine any time between mid-March and May, and more than 70% of Gaza's 2.3 million population is facing "catastrophic hunger."
Nearly half a million people remain trapped in northern Gaza, where people have resorted to eating animal feed in desperation, and at least 30 children have died of malnutrition in recent weeks.
Israel has waged a military offensive on the Gaza Strip since an Oct. 7 cross-border attack by the Palestinian group Hamas which killed around 1,200 people.
Around 33,500 Palestinians have been killed in Gaza since the war began.
Israel has also imposed a crippling blockade on the seaside enclave, leaving its population, particularly residents of northern Gaza, on the verge of starvation.
The war has pushed 85% of Gaza's population into internal displacement amid acute shortages of food, clean water and medicine, while much of the enclave's infrastructure has been damaged or destroyed.
Israel stands accused of genocide at the International Court of Justice (ICJ), which has urged it to do more to prevent famine in Gaza.