The Gaza health ministry reported 18 people killed in a strike on a house in Nuseirat refugee camp in central Gaza, and said other targets were hit up and down.
Israel pressed its war on Gaza on Saturday, with Palestinian authorities reporting heavy shelling in several cities hours after world powers demanded more aid be allowed into the besieged enclave.
Clouds of grey and black smoke rose over the southern Gaza city of Khan Younis after strikes in the morning.
The Gaza health ministry reported 18 people killed in a strike on a house in Nuseirat refugee camp in central Gaza, and said other targets were hit up and down the coastal strip.
The bombardments came after the UN Security Council approved a resolution demanding "immediate, safe and unhindered" deliveries of life-saving aid be rushed to Gaza "at scale". Members had wrangled for days over the wording.
At Washington's insistence, they toned down some provisions and avoided calling for a ceasefire that would stop the war.
It is still unclear what, if any, impact the vote will have on the ground, where Gazans have been forced into crowded shelters or tents, and are struggling to find food, fuel, water and medical care.
UN Secretary-General António Guterres said a "humanitarian ceasefire" is the only way for aid "to be effectively delivered".
The issue was not the number of aid trucks, he said, but "the way Israel is conducting this offensive is creating massive obstacles" to aid distribution.
Famine looms
Immediately after the UN vote, Israel again vowed to fight on until Hamas is "eliminated" and hostages are freed.
"Israel will continue the war in Gaza," said Foreign Minister Eli Cohen, insisting the war was legal and just.
Israel has launched a relentless bombardment and ground invasion of Gaza, where 20,057 people have been killed, mostly women and children, according to authorities in the strip.
Allies, including the United States which provides Israel with billions of dollars in military aid, have increasingly pressured Israel to avoid civilian casualties.
The UN estimates the fighting has displaced 1.9 million of Gaza's 2.4 million population.
World Health Organization chief Tedros Adhanom Ghebreyesus said a majority of those uprooted from their homes were now going "entire days and nights without eating", and "famine is looming".
Displaced again
A one-week truce that Qatar helped mediate, with support from Egypt and the US, ended on 1 December. It saw 80 Israeli hostages released from Gaza captivity in exchange for 240 Palestinians held by Israel.
Israel has repeatedly told Palestinians to make their way to areas in the narrow Gaza Strip it says are safe, but even when they do, residents say they have still been bombarded.
Many Gazans have been forced to move multiple times.
Among them is Nur Wahidi, a doctor originally from Gaza City in the north, now displaced again and working in Rafah, in Gaza's far south.
"Diseases are terrifyingly widespread, and there's a significant shortage of food," she said, a stethoscope draped over her lilac sweater.
On Friday, thousands fled central Gaza after an army evacuation order. It warned residents of Bureij, a refugee camp established about 70 years ago, to move "for their own security" towards Deir al-Balah city further south.
Donkey carts creaked with their belongings as they passed through the streets. Families pushed babies in prams and led elderly relatives through the crowd, packing winter blankets for the road ahead.
The UN agency for Palestinian refugees, UNRWA, said the latest evacuation order would effect more than 150,000 people.
"The Israeli army just orders people to move into areas where there are ongoing airstrikes," Thomas White, UNRWA's Gaza director, wrote on social media.
