Italian activist Vittorio Arrigoni
Ihab Ghussein, a Hamas Interior Ministry spokesman, said Saturday the suspects are still being interrogated and authorities are also searching for other militants from the al-Qaida-inspired group believed to have carried out the slaying.
Vittorio Arrigoni was kidnapped by members of a small extremist group on Thursday. Hamas forces found his body Friday.
It was the first such kidnap-slaying of a foreigner in the Gaza Strip since the militant group Hamas took power in the territory in 2007.
It highlighted the challenge that Iran-backed Hamas faces from smaller extremist factions in Gaza that see it as too pragmatic.