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.
The Israel Defence Forces (IDF) said on Wednesday that its strikes on Gaza were its largest since the conflict in 2014.
The Hamas-run health ministry in Gaza says that more than 300 people have been injured there since the conflict began, as well as the 53 who have died.
Hamas said it was incensed by "the enemy's targeting of residential towers".
Residents had been warned to evacuate the buildings before the fighter jets attacked, however health officials said there were still civilian deaths.
Sirens continued to sound in southern Israeli towns and cities on Wednesday afternoon after what the IDF described as a barrage of rockets was fired by Hamas.