Vittorio Arrigoni, 36, was kidnapped on Thursday morning by a group identifying itself as the Brigade of the Gallant Companion of the Prophet Mohammed bin Muslima. The radical Salafist group believes Hamas is too moderate and several of its members, including its leader Sheikh Abu Walid al-Maqdasi, are in prison.
In a video released on YouTube, the group described Arrigoni as a foreign journalist trying to spread corruption and called Italy "the infidel state".
They threatened to execute him unless the Hamas government released its jailed members by 5 pm (2 pm GMT) on Friday. It is not clear why they killed Arrigoni before their deadline.
His body was found hanging in an abandoned house in northern Gaza. Hamas says it has arrested two suspects and is searching for the others.
“The other members of the group will be hunted down and the law will be applied,” promised government spokesperson Ihab al-Ghoussein, who condemned the murder as “a heinous crime which has nothing to do with our values or our religion”.
The Italian foreign ministry expressed its “deep horror” at Arrigoni’s death, which it described as “act of vile and senseless violence committed by extremists who are indifferent to the value of human life”.
Arrigoni, who had been living in the Gaza Strip for almost three years, was a member of the International Solidarity Movement (ISM). The group campaigns against the Israeli occupation of Palestinian territories.
ISM co-founder Huwaida Arraf said Arrigoni was well-known in Gaza and praised his “dynamic, humanitarian personality”. The group is still discussing whether to advise its member to leave Gaza in the wake of his murder.