A Palestinian woman mourns a relative, killed in an Israeli strike, outside the al-Shifa hospital in Gaza City. AFP
The agency said the children were among 17 victims in a strike on Deir el-Balah.
According to the UN children's agency, the dead included a one-year-old boy whose mother said he had spoken his first words just hours earlier. The mother was critically injured, UNICEF added.
"No parent should have to face such tragedy," UNICEF executive director Catherine Russell said in a statement.
"The killing of families trying to access life-saving aid is unconscionable," she added.
US-based charity Project Hope, which runs the facility, said the victims were waiting for the clinic to open to receive treatment for malnutrition, infections and illness. The charity gave a toll of 15 dead, including 10 children and two women.
Its president and chief executive Rabih Torbay called the strike "a blatant violation of international humanitarian law."
Yousef Al-Aydi, 30, was among dozens of people -- most of them women and children -- in the queue.
"Suddenly, we heard the sound of a drone approaching, and then the explosion happened," he told AFP by phone.
"The ground shook beneath our feet, and everything around us turned into blood and deafening screams."
Mohammed Abu Ouda, 35, was also in the queue at Project Hope. "What was our fault? What was the fault of the children?" he asked.
"I saw a mother hugging her child on the ground, both motionless -- they were killed instantly."
Four people were killed and several injured in a separate pre-dawn air strike on a home in Al-Bureij camp in central Gaza, civil defence agency official Mohammed al-Mughair added.
AFP footage from Al-Bureij showed a family including three young children sitting among rubble outside their tattered tent after an air strike hit a house next door.
Elsewhere, three people, including a woman, were killed by Israeli gunfire on civilians near an aid centre in the southern city of Rafah, the civil defence agency said.
More than 600 people have been killed around aid distributions and convoys in Gaza since late May, when Israel began allowing a trickle of supplies, the United Nations said in early July.
The European Union on Thursday said it had struck a deal with Israel to open more crossings for aid, as well as to repair infrastructure and protect aid workers.
"We count on Israel to implement every measure agreed," EU foreign affairs chief Kaja Kallas wrote on X.
Since launching its war on Gaza on 7 October 2023, Israel has killed nearly 58,000 Palestinians, most of them women and children, according to Gaza’s health ministry. Thousands more remain missing under the rubble. Independent estimates suggest the true death toll could be closer to 100,000.
*This story was edited by Ahram Online.
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