Four people including a three-year-old boy, Yahya Al-Malahi, were killed in a strike that had targeted a police vehicle in Gaza City, the Hamas-run Interior Ministry said.
A police officer was among the dead, while nine bystanders were wounded, some critically, it said.
In the north of the enclave near Jabalia, Israeli fire killed a 14-year-old child, Adam Ahmed Halaa, health authorities and his family said.
Israel's military did not immediately provide comment on either incident on Tuesday local time.
Later in the day, an Israeli airstrike hit near a cafe in the Beach camp in western Gaza City, killing at least five people and wounding several others, health officials said.
An Israeli military spokesperson said the strike targeted a Hamas militant.
At Gaza's largest hospital, Al Shifa, relatives rushed to farewell those killed.
Carrying his little boy in his arms, Mukhlis Al-Malahi said they were leaving a relative's wedding when the Israeli plane attacked the police vehicle.
"We got close to Timraz crossroad with Nafaq (street); then, we suddenly found something hitting us. They hit a police vehicle as we walked," the father, whose shirt was stained with his son's blood, told Reuters.
"What is his fault? What is his crime? He should be wearing a wedding suit at his cousin's today, but instead, he wore a shroud stained with blood," cried the young boy's cousin, Hader Al-Malahi.
In northern Gaza, Israel's military said it killed a man who had approached the armistice line with Hamas, describing him as an armed militant.
Health authorities confirmed a man had been killed in the area, without providing details.
A ceasefire that began in October halted two years of full-blown war but left Israeli troops in control of a depopulated zone that makes up well over half of Gaza, with Hamas in power in the remaining, narrow coastal strip.
Israel has escalated its attacks on Hamas-led police and security forces since October, killing dozens, the group's officials in Gaza have told Reuters, accusing Israel of trying to cause chaos and anarchy.
Israel says it aims to thwart attacks by Hamas and other militant factions.
More than 750 Palestinians have been killed since the ceasefire deal took effect, while militants have killed four Israeli soldiers. Israel and Hamas have traded blame for ceasefire violations.
Palestinians also say Israeli forces have been expanding the zone they occupy. Israel denies this.
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