The deaths add to a toll of more than 1100 Palestinians killed by Israeli attacks since an October ceasefire between Israel and Hamas took effect, according to health officials in the enclave.
The truce halted major fighting but has failed to stop sporadic violence. Four Israeli soldiers have been killed by militants in Gaza over the same period.
Medics said Muataz Abu Shaar, 10, was shot on Tuesday by Israeli gunfire in Rafah, southern Gaza.
In Jabalia, in the north of the enclave, an Israeli air strike on a post of the Hamas-led police force killed at least seven people, including a woman, and wounded several other people, medics and police officials said.
The Hamas-led interior ministry said in a statement the dead included the head of the Jabalia police force, Colonel Mohammad Marwan Salem, along with other officers.
The Israeli military said in a statement it killed Salem, whom it described as the head of Hamas' central Jabalia battalion, along with three other militants of the group.
Those killed have in recent months gathered with the goal of planning and carrying out attacks, it added. "They were eliminated in order to remove the threat."
Israel wants Hamas to cede control of Gaza and disarm, and while the group said it was ready to relinquish power, it has always resisted calls to lay down arms.
Later on Tuesday, a Palestinian was killed and several others were wounded near a mosque in western Gaza City, medics said, taking Tuesday's death toll to at least 10.
The Israeli military did not immediately comment on that incident, nor the death of the 10-year-old boy.
In Khan Younis, in the south, an Israeli air strike killed a 36-year-old man and left three people wounded, medics said. The Israeli military said it struck a Hamas militant.
The latest violence comes as Hamas leaders visited Cairo for further talks on implementing the second phase of US President Donald Trump's Gaza peace plan.
The discussions include Hamas disarmament and Israeli army withdrawals, according to sources close to the talks, who said little progress had been made in the past weeks towards reaching a broad agreement to end the conflict.
Hamas says Israel's violations of the ceasefire are a key obstacle to implementing the second phase of Trump's plan.
Nearly all of Gaza's two million people, most of whom have been displaced several times, now live on a tiny strip of land along the coast, mainly in makeshift tents or damaged buildings, under Hamas control.
Hamas-led fighters killed 1200 people during their cross-border attack into Israel on October 7, 2023, according to Israeli tallies. The Gazan health ministry said more than 73,000 Palestinians have been killed in the territory since then.
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