Israel conducted dozens of airstrikes on the Gaza Strip on Monday, after Palestinian militants fired barrages of rockets at southern Israeli cities.
The pre-dawn raids on Gaza were some of the heaviest seen since the fighting began a week ago.
Israel said it hit facilities belonging to the militant group Hamas and several commanders' homes, but main roads and power lines were also damaged.
There were no immediate reports of casualties following the strikes.
People in Gaza have told of their fear. "I was getting ready to die. I had to be at peace with it," Najla Shawa, a Palestinian humanitarian worker and mother of two, told the BBC.
Describing previous airstrikes over the weekend, she said: "People we know [were killed], people we work with... ordinary people, professional people, young and old."
The Israeli military said more than 50 warplanes conducted a 20-minute attack on the Gaza Strip shortly before dawn on Monday.
They struck 35 "terror targets" and destroyed more than 15km (9.3 miles) of an underground tunnel network belonging to Hamas, it added.
The military also said it had hit the homes of nine "high-ranking" Hamas commanders. Israeli soldiers also fired artillery from positions near the Gaza border.
