The deadly exchange of fire between Palestinian militants in the Gaza Strip and the Israeli military has escalated significantly, with the UN fearing a “full-scale war”.
More than 1,000 rockets have now been fired by Palestinian militants over 38 hours, Israel said, most at Tel Aviv.
Israel has carried out hundreds of air strikes, destroying two tower blocks in Gaza on Tuesday and Wednesday.
At least 53 Palestinians and six Israelis have been killed since Monday.
That includes 14 Palestinian children caught up in the conflict.
UN Secretary-General António Guterres said he was “gravely concerned” by the ongoing violence.
An Israeli citizen was killed when an anti-tank guided missile, fired from the northern Gaza Strip, struck a jeep on the border. Three other people were injured.
The Israeli fatalities also reportedly include a 52-year-old father and his 16-year-old daughter who died in the city of Lod near Tel Aviv when a rocket hit their car.
In Gaza five members of one family were killed in an Israeli air strike. Streets are full of rubble where buildings have collapsed and cars have been left crushed or burned.
Israel says it has carried out operations to assassinate senior Hamas officials in Gaza.
Israeli Arabs have staged violent protests in a number of Israeli towns. Lod near Tel Aviv has been put under a state of emergency.
Prime Minister Benjamin Netanyahu said the government would use all its strength to protect Israel from enemies on the outside and rioters on the inside.