Medics and residents said an Israeli drone fired a missile at people who came out of their homes when an Israeli-backed Palestinian militia tried to storm an area east of Maghazi camp on Tuesday. As well as at least five fatalities, several people were injured.
Asked for comment on the incident around Maghazi camp, the military said troops identified what it described as "armed terrorists" near its armistice line with Hamas, and that they carried out a strike to remove the threat.
Incursions by Israeli-backed armed gangs, whom Hamas brands "Israeli collaborators", have escalated in past weeks.
Leaders of those groups, who operate in areas under Israeli control, say they aim to topple Hamas rule.
Later on Tuesday, an Israeli air strike struck a vehicle in the southern Gaza city of Khan Younis, killing two people and wounding several others, medics said.
The Israeli military told Reuters it was a "targeted strike" and provided no further details.
An October ceasefire, brokered by US President Donald Trump, has failed to halt Israeli attacks in Gaza.
Israel and Hamas are deadlocked in indirect talks over implementing the second phase of the deal, which includes the group's disarmament and Israeli army withdrawals.
The ceasefire left Israel in control of more than half of Gaza, with Hamas controlling a sliver of coastal territory.
Some 900 Palestinians have been killed in Israeli strikes since the truce came into effect, according to figures from Gaza health officials that do not distinguish between combatants and civilians.
Four Israeli soldiers have been killed by militants during the same period, the country's military has said.
Hamas does not disclose figures for casualties among its fighters. Israel says its post-ceasefire strikes are aimed at preventing attacks or stopping people from approaching its armistice line with Hamas.
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