Jabari, nicknamed Abu Mohammed, was born in 1960 in the eastern Gaza neighborhood of Shejaiya. In 2006, he became the acting commander of the military wing of Hamas after his predecessor, Muhammad Deif, was seriously wounded in an Israeli attack.
Jabari began as a member of Palestinian President Mahmoud Abbas' Fatah party, but switched his allegiance to Hamas after serving 13 years in an Israeli prison.
He survived four previous attempts by Israel to kill him. In one attempt in 2004 his eldest son, his brother and three other relatives were killed.
He was said to have led the bloody 2007 takeover of Gaza from Fatah forces, developing Hamas's military arsenal and its networks in Iran, Sudan and Lebanon and for his planning of the Schalit kidnapping. Hamas has ruled Gaza with an iron grip since then, and repeated attempts to reconcile with Fatah have failed.
The assassination threatened to further damage Israel's relations with Egypt, which is governed by Hamas' ideological counterpart, the Muslim Brotherhood.
On its official Facebook page, the Freedom and Justice Party, the Muslim Brotherhood's political arm, called the assassination a "crime that requires a quick Arab and international response to stem these massacres against the besieged Palestinian people in the Gaza Strip."
It accused Israel of trying to "drag the region toward instability."
Israel and Egypt signed a peace accord in 1979. Relations, never warm, have deteriorated since longtime Egyptian President Hosni Mubarak was ousted in a popular uprising last year.
Heller reported from Jerusalem. Additional reporting from Sarah El Deeb in Cairo. Follow Heller on Twitter (at)aronhellerap
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