The attacks came just before dawn.
One of Gaza's tallest structures, a 13-storey apartment and office tower was destroyed, along with most of a 16-floor residential building.
The Israeli military says it attacked 15 sites, including some in buildings it says housed Hamas command and control centers.
At sun rise, residents returned to survey the damage. This man says the Israeli Defense Forces called his neighbor to warn him of strikes:
(SOUNDBITE) (Arabic) RESIDENT OF BUILDING KNOWN AS "ITALIAN", MOHAMMED LUBAD, SAYING:
"They told him that after the third one, no one should be around the area of the building, because they will strike the building. They said - do not count the strikes, and do not come back to the area."
The warnings appear to have prevented any fatalities, although at least 20 people were wounded in the attack on a building known as the Italian Complex.
Hamas is accusing Israel of an unprecedented act of revenge against civilian
