Palestinians in the Strip fear that the incident would raise the tension between Hamas and Fatah and lead to additional violent incidents between the different factions.
The man, Hisham Mukhaimar, a member of Hamas' Popular Resistance Committees, was arrested on suspicion of being involved in the murder Monday of three schoolboys whose father was an intelligence official considered close to Palestinian President Mahmoud Abbas.
The days of mourning the three children ended Thursday.
A Hamas spokesman said that "anyone who will be found guilty of the children's deaths deserves to die, even if he is a member of the Popular Resistance Committees.
However, a PRC spokesman demanded Mukhaimar's immediate release and threatened
retaliation if he was not set free.
"The PRC condemns the arrest by tens of masked men from the General Intelligence of a member of the PRC after they threw hand grenades and opened fire at his house," Abu Amir said.
The violent clashes between the Palestinian factions in the Strip have been going on for several days now. On Wednesday, two Hamas activists were injured after a Fatah member hurled a hand grenade at a rally held by the movement in the Nuseirat refugee camp in the central Strip.
Palestinian sources in the strip reported Wednesday evening that many Fatah members deployed in several places in the Strip and began shooting in the air.