The deadly incident occurred when Hamas' police engineering team attempted to disable the Israeli missile that hit near the al-Sheikh Zayid towers in Beit Lahiya town days earlier, but did not explode.
The journalist, identified as Simone Camilli, 35, was at the scene reportedly to cover the work to defuse the ordnance. He is the first foreign journalist killed in the Gaza conflict.
The bodies and the injured were taken to an area hospital, said Ashraf al-Qidra, spokesman for the Gaza Health Ministry.
A Palestinian photojournalist, Hatem Moussa, was also injured in the explosion.
Nearly 2,000 Palestinians have been killed in Gaza in Israel's Operation Protective Edge that started on July 8. An intensive talks to find a more permanent end to over a month-long violence is currently underway in Cairo.
The 72-hour ceasefire ends at midnight tonight and Palestinian militant factions have warned that they will not extend it and start fighting if their key demands are not met.
At the centre of eight points demand placed by the militant factions is the removal of blockade over Gaza that the Palestinians say has crippled their economy, putting them under siege, and amounts to collective punishment.
Media reports suggest Israel may ease some restrictions but it will be limited in scope to check Hamas and other militant factions from acquiring more arms.
A failure to extend the three-day lull risks a resumption of five weeks of bloody fighting that has killed more than 1,950 Palestinians, 64 Israeli soldiers and three civilians in Israel.
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