Gaza's Hamas rulers on Saturday executed a Palestinian convicted of collaborating with Israel and two others deemed complicit in murder, an interior ministry statement said.
It said the three men were hanged in a "security centre" in Gaza City.
It was the first time this year that the Islamist movement had carried out an execution of someone accused of "collaborating" with the Israelis.
The ministry statement did not give the men's names, ages or any other information.
However, Hamas security sources identified the "collaborator" as Mohammed Garboh from Bureij refugee camp, and the other two men as Mohammed Abdeen from Khan Yunis and Mohammed Baraka of Deir al-Balah.
London-based human rights organisation Amnesty International said on Thursday that a fourth man was currently on death row.
The last time the death sentence for aiding Israel was carried out was in July 2011, when two Palestinians were executed on the charge.
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A month later, three more people were executed on charges unrelated to collaboration, rights groups say.
Israeli security forces routinely use Palestinian informers to thwart militant attacks and assist in the assassination of top militants.
In March, a military court in Gaza condemned to death a 27-year-old Palestinian convicted of "treason" for allegedly cooperating with Israel, but did not publish his name.
Since the start of this year, the authorities in Gaza have announced two other death sentences, one against a man convicted of collaborating with Israel and the other found guilty of killing his brother.
It was not clear if either or both of those were hanged on Saturday.
Under Palestinian law, collaboration with Israel, murder and drug trafficking are all punishable by death.
All execution orders must be approved by the Palestinian president before they can be carried out, but Hamas no longer recognises the legitimacy of Mahmud Abbas, whose four-year term ended in 2009.
In recent months, Hamas has arrested several alleged collaborators, and warned it would prosecute any "traitor" working for the Jewish state.