Palestinian health officials said one man was killed in an air strike on a car in the Khan Younis area in the south of the enclave while medics said two adult brothers were killed in Shujiaya, a neighbourhood east of Gaza City.
The Israeli military did not immediately respond to a request for comment on the two air strikes.
The military has killed more than 680 Palestinians in the Gaza Strip since a ceasefire with Hamas came into effect in November, local health officials say.
More than 72,000 have been killed since the war started in October 2023.
Israel is now also waging a war alongside the US against Iran, and is carrying out a new campaign against Hezbollah where Israeli forces have invaded southern Lebanon.
The Hamas-affiliated Shehab News Agency said the brothers were killed in an air strike by the Israeli military after an Israeli-backed Palestinian militia in the Gaza Strip had tried to abduct them.
Neither Hamas nor any other militant group has identified the brothers as members.
Witnesses told Reuters the two brothers, armed with guns, clashed with the militia and that they were later targeted by drones.
The witnesses also reported Israeli tanks opening fire.
Violence in the Gaza Strip has persisted despite the ceasefire and amid Israel's war with Iran.
Health officials in the territory say at least 40 Palestinians have been killed by Israeli forces since the Iran conflict began a month ago.
