The building housed the offices of the Associated Press and Al Jazeera collapsed after being struck by Israeli missiles.
The owner of the building had been warned in advance of an impending Israeli missile strike, a Reuters reporter said, and the building had been evacuated.
Israel has pummelled Gaza with air strikes whilst Palestinian militants launched rocket barrages at Tel Aviv and other cities today with no sign yet of an end to the worst escalation in years in the region, almost a week into the conflict.
US and Arab diplomats are seeking to calm the situation.
Violence overnight saw militants fire about 200 rockets at cities in Israel, whose planes struck what it said were targets used by Hamas, the Islamist group that runs Gaza.
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