Gaza's health ministry said Wednesday war with Israel has killed more than 21,000, as Israel kept pounding the besieged territory with air strikes and shelling.
The World Health Organization (WHO) said Gazans were in "grave peril" after more than 11 weeks of fighting, which left most hospitals in the Palestinian territory out of action and led to "acute hunger".
Explosions lit up the sky over the southern Gaza city of Khan Yunis -- a focus of heavy urban combat since the Israeli army said it had largely gained control over Gaza's north.
The Gaza health ministry said a strike hit a house near Al-Amal hospital in Khan Yunis, killing 22 people. Heavy firefights also raged again around Gaza City in the north.
Gaza's spiralling humanitarian crisis has amplified calls for an end to the hostilities.
WHO chief Tedros Adhanom Ghebreyesus called on the international community to take "urgent steps to alleviate the grave peril facing the population of Gaza and jeopardising the ability of humanitarian workers to help" the many in need.
In a statement, the WHO said "hungry people again stopped our convoys... in the hope of finding food".
"WHO's ability to supply medicines, medical supplies, and fuel to hospitals is being increasingly constrained by the hunger and desperation of people en route to, and within, hospitals we reach."
Israel has repeatedly vowed to keep up the campaign to destroy Hamas.
At least 21,110 people have been killed, according to the latest toll issued by Gaza's health ministry. It said 8,800 of them were children and 6,300 women.
The war has raised fears of a broader regional conflagration, with deadly exchanges between Israel and Lebanon's powerful Hezbollah movement, and Iranian calls for revenge after a strike blamed on Israel killed a senior general.
Gaza's 2.4 million people have suffered severe shortages of water, food, fuel and medicines, with only limited aid entering the territory.
An estimated 1.9 million Gazans have been displaced, the UN says.
AFPTV footage showed Palestinians who had been sheltering in a UN-run school in central Gaza's Nuseirat refugee camp fleeing south, seeking safety from the bombardment.
Displaced Gazans "don't know where to go", said one who declined to be named. "First, we're displaced to Nuseirat, then to Rafah."
Even schools "are no longer safe".
"A solution must be reached... Implement a ceasefire instead of bringing in aid," he added.
Palestinian president Mahmud Abbas charged in a television interview that the war "goes beyond a catastrophe and a genocide".
"Netanyahu's plan is to get rid of the Palestinians and the Palestinian Authority," said Abbas, who is based in the occupied West Bank.
The UN Security Council called in a resolution last week for the "safe and unhindered delivery of humanitarian assistance at scale".
The resolution, which did not call for an immediate end to the fighting, effectively leaves Israel with operational oversight of aid deliveries.
In the far-southern city of Rafah, hundreds turned up at the Abdul Salam Yassin water company with baskets, handcarts and even a wheelchair stacked with empty bottles to get clean water.
"This was my father's cart," said Rafah resident Amir al-Zahhar. "He was martyred during the war. He used it to transport and sell fish, and now we are using it to transport fresh water."
Elsewhere in Rafah, people split logs and stacked kindling as the lack of fuel forced them to burn wood for cooking and to keep warm.
Internet and telephone services that were cut on Tuesday were gradually being restored in central and southern areas of Gaza, the Palestinian telecommunications company Paltel said.